Road pricing is one solution to congestion not a "stealth tax", Tony Blair has told 1.8 million motorists.
The prime minister this morning began responding to drivers who signed the e-petition calling on the government to "scrap the planned vehicle tracking and road pricing policy".
Mr Blair stressed that no decision had been made on a national road pricing scheme, promising that the public and parliament would both be given the opportunity to contribute to the debate.
However, he insisted that road pricing must be considered as one solution to tackling congestion. Improving traffic flow and continued investment in public transport will not alone ease the pressure on the UK's road networks, the prime minister warned, with congestion predicted to increase by 25 per cent by 2015.
"We have a difficult choice to make about how we tackle the expected increase in congestion," Mr Blair told campaigners. He argued that the UK needs to "explore the contribution road pricing can make to tackling congestion."
Mr Blair argued: "It would not be in anyone's interest, especially those of motorists, to slam the door shut on road pricing without exploring it further."
Downing Street has rebuked many of the arguments levied against road pricing, including a 'myth buster' with the prime minister's email. It also refuted the costs cited by campaigners, arguing it is not yet possible to produce any credible estimates.
However, the Conservatives have urged motorists to treat Mr Blair's response with "extreme scepticism". Shadow transport secretary Chris Grayling said that he does not believe the government's claim that road pricing is not a stealth tax.
Mr Grayling claimed: "I know from extremely good sources that Gordon Brown and his team have had discussions about the possibility of using the revenue from road pricing to fill future black holes in public finance."
The Liberal Democrats also said that many motorists would remain unconvinced by Mr Blair's reassurances on cost. Transport spokesman Alistair Carmichael argued that the government needs to convince the public that road pricing would be a different tax, not an extra tax, concluding that Mr Blair's email "demonstrates a lack of leadership".
Paul Watters, head of public affairs at the AA, said that drivers were "rightly concerned" about any additional motoring costs. However he did not rule out road pricing as a solution.
"If congestion can be eased and investment improved by a fair and totally transparent realignment of how we pay for our motoring, it is worth serious discussion," he said.
Mr Blair's email also reassured motorists that it will be at least a decade before any national road pricing scheme is technically or politically possible.
He did confirm that the government is currently working with some local authorities with an interest in local road pricing schemes, needed to address localised congestion problems. However, Mr Blair insisted that no area would have a pilot scheme forced on it and any funds raised would be reinvested in local transport solutions.
Friends of the Earth has welcomed the road pricing debate, although warns that road pricing alone will not relieve congestion. Executive director Tony Juniper said: "Most people agree the UK's roads are in a mess with too much congestion and pollution. And most motorists agree we need to do something about it.
"It's good we're debating what to do. Road pricing isn't a magic solution, but it does have an important role to play."