SCOTTISH Labour’s first MP in a same-sex marriage has criticised Theresa May’s deal with the Democratic Unionist party ahead of today’s Edinburgh Pride march

Rutherglen & Hamilton West MP Ged Killen, who married his husband Peter in 2013, said he had fought for equality all his life as a Labour activist and would carry on in the Commons.

“I hope the DUP are offended by my arrival in Parliament,” he said.

The Prime Minister has been widely criticised for trying to strike a “confidence and supply” deal with the DUP since losing her majority at the election.

The ultra conservative party has repeatedly blocked gay marriage for Northern Ireland.

DUP leader Arlene Foster said last year that advocates of same-sex marriage were likely to send her “in the opposite direction”, while Ian Paisley Jr, the son of DUP founder Ian Paisley, has called homosexuality “immoral, offensive and obnoxious”.

Former Tory Prime Minister Sir John Major has also warned a Tory-DUP pact could destabilise the peace process, as the UK government would no longer be seen as an honest broker.

Mr Killen said he would use his speech to the Pride event in the capital to celebrate progress on LGBTI rights law, while warning Mrs May not to roll back on it to please the DUP.

He said: “In my lifetime we have seen off Section 28 and its equivalent in Scotland, equalised the age of consent, made civil partnerships a reality and then achieved marriage equality.

“But we cannot be complacent. For many LGBTI individuals around the world things are getting worse. And here at home, we have a Prime Minister doing a grubby deal with the DUP, a party that has consistently opposed gay rights in Northern Ireland.

“I have a clear message to both the DUP and the Tories: if you try to roll back any of the achievements we have made in LGBTI rights, in any part of the UK, you will have to deal with me and thousands of others like me standing in your way.”