A "quadruple lock" will safeguard religious organisations from legal challenges after the legalisation of gay marriage, the culture secretary has pledged.

Maria Miller told the Commons the coalition would protect religious freedoms while giving same-sex couples the chance to "enjoy the benefits" of marriage.

The safeguards pave the way for primary legislation in the new year which could come into force by 2014, but it is not yet clear whether the measures offered by the government will placate opponents.

"In each century parliament has acted, sometimes radically, to ensure marriage reflects our society, to keep it relevant and meaningful," Miller said.

"Marriage isn't static, it has evolved, and parliament has chosen over the centuries to make marriage more equal and fair. We now face another such moment – another such chance in the new century."

The government claims the chances of a successful legal challenge in the European court of human rights (ECHR) is "negligible" – a point of view clashing with that of the Church of England, which fears it could be vulnerable if it refuses to solemnize gay marriages.

Miller's "quadruple lock" will offer "clear and unambiguous protections" against the ECHR, which she pointed out puts protection of religious beliefs "beyond doubt".

It will become illegal for any religious organisation or individual minister to be forced to marry same-sex couples. Instead both religious organisations and individual ministers will have to expressly opt-in.

The Church of England will be explicitly protected by making it illegal for the institution to marry same-sex couples. "This recognises and protects the unique and established nature of these churches," Miller added.

Equality legislation will also be amended so no discriminatory claims can be brought.

Opposition to gay marriage from the Tory backbenches poses a big headache for the prime minister's leadership credibility.

But Conservative MPs are struggling to fend off attacks from the left over allegations of homophobia. David Davies, the MP for Monmouth, rejected claims he was bigoted by saying he once fought a gay boxer, Charles 'Pink Pounder' Jones.

"I think most parents would prefer their children not to be gay, knowing most parents want grandchildren if nothing else," he told BBC Radio Wales.

Shadow equalities minister Yvette Cooper welcomed the move, setting up the prospect of a vast Commons majority in favour of the reforms. That could frustrate opponents, who responded to the government consultation in vast numbers.

Ministers received 19 petitions and a record 228,000 submissions from individuals and organisations, Miller said.