A government minister has said Conservative MPs who signed a rebellious letter over Europe are “thick” – and believes several were doing it to get back at Prime Minister David Cameron for legalising equal marriage.

The comments suggest the Tory rift on equal marriage has not yet fully healed. 128 Conservative MPs voted against the Marriage (Same Sex Couples) Act as part of its third reading last year – only 117 Conservative MPs voted in favour. 

The unnamed minister told the London Evening Standard: “A number of the 90 are the ‘outers’ who want the UK to leave the EU no matter what. Others are hoping they will be able to push the Prime Minister into a tougher position.

“But there are also the thick, who won’t have grasped exactly what it was they were signing or will have been told by colleagues the letter was something other than it was. It’s fair to say that it might also have been used as a surrogate for some who were still upset over same-sex marriage.”

In response, Conservative MP Peter Bone said: “The idea that MPs signed without knowing what it was is ridiculous. When you sign a letter that is going to the Prime Minister you obviously make sure you know what it is. It’s not just the right of the party that are behind this.”

Mr Bone, MP for Wellingborough in Northamptonshire, was a key critic of David Cameron’s decision to legalise equal marriage for England and Wales. He suggested last March that the Church of England should respond to the pending arrival of equal marriage by saying, “marriage is between a man and a woman so this is completely nuts”.

In November, Mr Bone withdrew his private member’s bill for a referendum on the issue.

With equal marriage now law, Mr Bone told PinkNews.co.uk that there was “no point in trying to change it now”.

He conceded “we didn’t win” and that equal marriage opponents would instead be waiting to see what happens when the first same-sex weddings take place in March.

The Same Sex Marriage (Referendum) Bill 2013-2014 had been tabled by Mr Bone as part of an “alternative Queen’s Speech” by backbench Tories.

When the Queen gave Royal Assent to the Marriage (Same Sex Couples) Act, David Cameron wrote for PinkNews.co.uk. In his article he said: “I am proud that we have made same-sex marriage happen. I am delighted that the love two people have for each other – and the commitment they want to make – can now be recognised as equal. I have backed this reform because I believe in commitment, responsibility and family. I don’t want to see people’s love divided by law.