Suffolk peer Lord Deben has thrown his weight behind the Prime Minister’s gay marriage bill warning it would be wrong to hinder a “measure whose time has come”. The former Suffolk Coastal MP’s intervention comes as ministers are braced for a new battle over plans to allow gay marriage.

The legislation, which divided the Conservative Party in the House of Commons, today begins what is expected to be a bruising passage through the House of Lords.

Peers from all parties are set to unite in a bid to derail the controversial move, with Prime Minister David Cameron under pressure from Tory activists to abandon the reform.

Lord Deben is one of six former ministers who argued in the letter to The Times that the allowing same-sex marriage would strengthen the institution.

It said: “We believe it is right to open up marriage to loving and committed same sex couples, and that this important institution will be strengthened by the change. The bill rightly enshrines the principle of religious freedom, protecting faith groups that do not wish to conduct same-sex marriages, but allowing others to do so if they wish.”

Some 86 members of the upper house have asked to speak in the second reading debate on the Marriage (Same Sex Couples) Bill, forcing the government to delay a vote to avoid a potential defeat.

It was postponed to later tomorrow amid fears opponents were more likely to stay on into the early hours in the hope of killing off the bill.

Mr Cameron has personally championed same-sex marriage in the face of vehement opposition from many in his own party and church leaders.

More Conservative MPs voted against it than for in the Commons, but Labour and Liberal Democrat support meant it was eventually passed by a majority of 205 in a free vote following a highly-charged debate.

The Tory leader has made efforts to calm tensions with party members over the issue but remains under serious pressure to make a U-turn.