On 5 June 1975, the United Kingdom voted decisively to remain a member of the European Economic Community (EEC or Common Market) in the country’s first-ever nationwide referendum. A resounding 67.23% voted in favour of staying in, versus 32.77% who supported withdrawal.

The referendum was called by Harold Wilson’s Labour government – largely to resolve deep internal divisions over Europe.

Labour’s February 1974 and October 1974 general election manifestos had promised to renegotiate the terms of membership, secured by Edward Heath’s Conservative government in 1973, and to put the outcome to a vote. Labour’s conversion to a referendum policy came in 1972, when the party leadership supported an amendment to the European Communities Bill (proposed by Conservative MP Neil Marten) which called for a consultative referendum on British entry. This decision, a concession to Labour’s eurosceptic tendency, led to the resignation of Roy Jenkins as deputy leader of the Labour Party.

Across two summits in 1974 and 1975, the UK government negotiated with the other eight member states the introduction of an EEC regional policy, a budgetary correction mechanism and market access for dairy products from New Zealand.

On 5 June 1975, the question that appeared on the ballot paper was as follows: “The government has announced the results of the renegotiation of the United Kingdom’s terms of membership of the European Community.

“Do you think the United Kingdom should stay in the European Community (the Common Market)?”

Peter Kellner, a political analyst and pollster, has argued that the decision to hold the 1975 referendum “was a constitutional outrage” in that “it was wholly to do with holding the Labour Party together”.

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During the campaign, the normal rules of party politics were summarily suspended. Wilson granted his ministers a rare ‘agreement to differ’, summarily suspending collective responsibility.

Speaking in the House of Commons in January 1975, Wilson said cabinet ministers would be “free to support and speak in favour of a different conclusion in the referendum campaign”. The prime minister confirmed that the government would make a determination as to its position – “whether for continued membership of the Community on the basis of the renegotiated terms, or for withdrawal” – following the conclusion of the renegotiation period.

Some weeks later on 18 March, Wilson announced the government’s support for “staying in the community”. The prime minister delivered an “assessment of what has been achieved” during the negotiations, arguing that he had fulfilled Labour’s manifesto objectives.

Wilson stated that the “vital interests of individual nations are now getting much more of a fair hearing, and the political power in asserting those interests has certainly increased” as a result of the negotiations.

In the end, of the 23 members of Wilson’s cabinet, seven did not support the government’s pro-EEC position.

The prime minister nonetheless made plain that the freedom provided to ministers in opposing official government policy did not extend to parliamentary proceedings. Eric Heffer, the minister of state for industry, was forced to resign after he fell foul of this rule, after speaking against the government position in a commons debate.

Heffer’s speech came during a debate on 9 April, concerning a motion that approved “the recommendation of Her Majesty’s Government to continue Britain’s membership of the community.”

In his contribution, Heffer told MPs that the guidelines of the Common Market were as “unacceptable as the guidelines on the question of ministerial discussion in the House.” He argued that there had been no “fundamental renegotiation” and referred to the “encumbrance of the EEC commission, to determine our own aids to industry”

The minister concluded: “I am convinced that [the British people] will vote ‘No’ in the coming referendum, and they will be right to do so.”

The government’s pro-EEC motion was passed ultimately by 396 votes to 170 because of the overwhelming support of Conservative and Liberal MPs. But more Labour MPs voted against continued membership of EEC than voted in favour (by 11).

On 26 April, a special one-day conference of the Labour Party voted decisively for the United Kingdom’s withdrawal from the EEC. The position was carried by 3,724,000 votes to 1,986,000 – almost a 2:1 margin.

The outcome meant that every major organ of the Labour Party was now pitted against the government’s policy. On 26 March, mere days after Wilson’s statement in the commons recommending “remain”, Labour’s national executive committee (NEC) had resolved in favour of withdrawal.

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The “Yes” campaign, officially the Britain in Europe (BIE) campaign, was a cross-party effort – led by the prime minister and most of his cabinet, the Conservative Party under its new leader Margaret Thatcher, and the Liberal Party. It argued that membership was vital for jobs, trade and Britain’s influence in the world.

Thatcher had previously expressed opposition to Labour’s referendum policy, and the Conservatives voted against the Referendum Act 1975. In March, Thatcher referred to the plebiscite as “a device of dictators and demagogues”.

But during the campaign, Thatcher expressed her support for the pro-EEC position. In a speech on 19 April, launching the Conservative Party’s referendum campaign, Thatcher invoked Disraeli, Churchill and Macmillan in making the case for Europe.

She stated: “We are inextricably part of Europe. Neither [Michael] Foot nor [Tony] Benn nor anyone else will ever be able to take us ‘out of Europe’ , for Europe is where we are and where we have always been.”

Standing alongside Edward Heath, whom she supplanted as Tory leader, Thatcher praised the former prime minister for his “endeavours, enthusiasm and dedication” in securing Britain’s place in Europe.

Thatcher added: “Conservatives must give a clear lead and play a vigorous part in the campaign to keep Britain in Europe to honour the treaties which you, sir, signed in Britain’s name.

“We must do this, even though we dislike referenda. We must support the prime minister in this, even though we fight the government on other issues.

“We must play our full part in ensuring that Conservative supporters say ‘Yes to Europe’.”

The “No” campaign, officially the National Referendum Campaign (NRC), was championed by senior Labour cabinet ministers, including Benn and Foot, as well as the leading former Conservative figure Enoch Powell. During the February 1974 election campaign, Powell urged voters to support Labour over its referendum promise. He said it was people’s “national duty” to oppose those who had deprived parliament of “its sole right to make the laws and impose the taxes of the country.”

The central conflict of the campaign was provided by Jenkins, the europhile home secretary, and Benn, the eurosceptic industry secretary.

During the campaign, Benn delivered the contested claim that being in the EEC had cost the country half a million jobs. Jenkins dismissed the suggestion in a press conference of his own.

The home secretary stated: “I find it increasingly difficult to take Mr Benn seriously as an economics minister.”

Some days later, on 2 June 1975, Jenkins and Benn clashed in a BBC Panorama TV debate. The debate, watched by a reported 8 million people, represented a more sober discussion of the merits of the campaign.

In one exchange, Benn argued that EEC membership meant surrendering the liberty to decide Britain’s policies through the ballot box in return for economic gain. Jenkins pushed back, drawing a distinction between “sovereignty” and “liberty”.

Benn responded: “We give up the liberty to decide our policy through the ballot box in pursuit of some economic advantage.”

The industry secretary also expanded on his claim that 500,000 jobs had been lost as result of Britain’s membership of the common market. He argued that all the evidence “of our eyes confirms it in the Midlands, in Merseyside, in Scotland and elsewhere, that common market membership has been a disaster.”

He added: “Our future lies, as we’ve argued, it does, in increasing our trade with the rest of the world.”

Jenkins rejected Benn’s argument as “nonsense”.

He stated: “How Tony Benn can discuss these issues of jobs and employment without any regard either to the blow to the prosperity of the Western world as a whole as a result of the oil prices, or without any regard at all to the dangerous rate of inflation in this country, I do not know.”

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The result was an overwhelming endorsement of continued membership. Every administrative region of the UK voted ‘Yes’, with the exception of the Shetland Islands and the Western Isles. The turnout was 64.62%.

Wilson hailed the result as a “historic decision”.

Speaking outside 10 Downing Street on the evening of 6 June, the prime minister stated: “The British people in clear and unmistakable terms have made their historic decision that Britain shall remain a member of the European Community.

“They have overwhelmingly supported the government’s recommendation.

“Their verdict has been given by a vote and by a majority bigger than that achieved by any government in any general election in the history of our democracy. No one in Britain, in Europe, or the wider world should have any doubts about its meaning.”

Jenkins responded: “It puts the uncertainty behind us. It commits Britain to Europe; it commits us to playing an active, constructive and enthusiastic role in it.”

Heath said: “I’ve worked for this for 25 years, I was the prime minister who led Britain into the community and I’m naturally delighted that the referendum is working out as it is.”

Benn responded: “When the British people speak everyone, including members of parliament, should tremble before their decision and that’s certainly the spirit with which I accept the result of the referendum.”

Helmut Schmidt, chancellor of West Germany, said: “A Europe without Britain would not have been strong enough.”

Wilson delivered a statement on the referendum result in the House of Commons on 9 June.

The prime minister recognised the “deep sincerity with which views have been held on both sides.”

But he added: “The debate is now over. The two tests set out in our manifesto of successful renegotiation and the expressed approval of the majority of the British people have been met.

“The historic decision has been made. I hope that this House and the country as a whole will follow the lead which the government intend to give in placing past divisions behind us, and in working together to play a full and constructive part in all community policies and activities.”

The referendum effectively settled the European question in British politics – at least until 2016.

The decision reached by the British electorate in 1975 was ultimately overturned by the 2016 referendum on the United Kingdom’s membership of the European Union (EU) and the European Union (Withdrawal Agreement) Act 2020.