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The day of the Northern Ireland same-sex marriage bill began with a gathering of MPs and supporters from across parties for a photo call to show their support for the bill.

This was a happy gathering with supporters sharing their optimism and offering their support and best wishes to Conor McGinn for the introduction of his bill later that day.

Conor made a powerful, humorous and emotive speech in support of his bill which passed unanimously with the DUP MPs in Parliament not even showing their faces in the chamber when the bill was read.

Conor’s bill is a Ten Minute Rule Bill. This type of bill is a method by which MPs can introduce legislation into the House of Commons. If it passes the first stage, as Conor’s bill has today, it is considered to have passed its first of three required readings. The second is scheduled for May 11.

Unfortunately, despite the support, the bill has little chance of becoming law. This is because, whilst a Ten Minute Rule Bill enters the law-making process, it rarely gets the time to pass all the necessary stages it needs to be given Royal Assent and become law before the end of the Parliament, at which point any uncompleted bills fall and then have to be restarted.

If left alone this is the likely fate of the Northern Ireland same-sex marriage bill. However, the Government can schedule time for the bill to become law, meaning its fate is ultimately in the hands of the Prime Minister.

Related: UK Parliament advances bills to bring equal marriage to Northern Ireland

I asked the Prime Minister at PMQs today whether she would stop hiding behind the DUP and put on record her support for the proposed legislation. She did not rise to the challenge. In her answer, she tried to state her party’s record on LGBT rights while in the next breath refusing to offer her support for their advancement in Northern Ireland.

Her response indicates that the UK Government is still in the pockets of the DUP on this issue and will be reluctant to give the bill time to be fought out in Parliament. Both the Prime Minister and the DUP know that they will lose this fight, so have chosen to run away.

Campaigners for Same Sex Marriage such as Love Equality NI rightly point out that this is not the end but one further step which marks the beginning of the end of marriage discrimination in Northern Ireland.

This bill should be a rallying call for campaigners for equal marriage to put pressure on MPs to force the Government to a vote on this bill. The Government is inherently unstable and, with her slim majority, just 10 Tory MPs need to be convinced to break ranks to overturn the DUP deal and the day will be won.

There are many Tory MPs I know who support this bill. It is time they used their position within the Conservative Party to gain the ear of the PM and it is up to us to convince them to do so.

On my own patch in Scotland, one such example is the leader of the Scottish Conservative Party, Ruth Davidson. I do not doubt her commitment to marriage equality in Northern Ireland. However it’s time she put her money where her mouth is. She once said that “there were a number of things that count to me more than the party; one of them is country, one of the others is LGBTI rights.”

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There are 13 Scottish Conservative MPs, many of whom supported the bill today and were at the gathering of supporters in the morning.

I and supporters of equal marriage are today throwing down the gauntlet to those Conservative MPs who are on the right side of history and issuing a challenge: let’s bring the bill back to Parliament for a vote and make sure that no-one in Northern Ireland must wait for the DUP to decide when they get their rights.

Ged Killen is the Scottish Labour & Co-op MP for Rutherglen & Hamilton West