Conservative MPs, including members of the Government itself, are set to be given a free vote on whether same-sex couples should be allowed to marry.

It had been understood that backbench MPs would be given a free vote, but this has been extended to Cabinet and junior ministers after a major rebellion by ministers, according to The Daily Telegraph.  

Downing Street initially suggested that members of the Government would be required to support the plans when the proposals are debated in the Commons.

However, after a series of senior government figures expressed their dismay at the development, Number 10 sources pledged to allow MPs to vote with their consciences.

Gerald Howarth, a defence minister, welcomed the decision, saying last night that it was “absolutely right and proper” for MPs to be allowed a free vote.

A formal consultation on how civil marriage will be reformed was launched earlier this year.

The Prime Minister has made a personal commitment to reform the law to allow same sex couples to wed, insisting that stable family relationships deserved support regardless of their composition.  

But senior Conservatives privately believe the policy is a Liberal Democrat-inspired distraction from more urgent tasks, such as addressing unemployment and securing the economic recovery.

On Tuesday, Northern Ireland Secretary Owen Paterson emerged as the first Cabinet Minister to break ranks over the Government’s controversial plans to redefine marriage.

He revealed his position in response to correspondence from a homosexual constituent.  

In a letter to a constituent last week, Mr Paterson said he supported other measures taken to increase the rights of homosexuals in Britain and around the world.

However, he said after “having considered this matter carefully” he had “come to the decision not to support gay marriage”.

Other ministers who have signalled their concerns over the issue in recent weeks include Philip Hammond, the Defence Secretary, Tim Loughton, the children’s minister, and Mr Howarth.

On Wednesday night, Mr Howarth, a committed Christian who is opposed to same-sex marriage, told The Daily Telegraph he had been personally “assured” that MPs would be allowed a free vote.

“These issues are traditionally conscience issues,” he said. “There is a long-established principle. I am sure that that will be understood.”

The move came after the Prime Minister’s Official spokesman indicated yesterday that the doctrine of “collective responsibility”