Opponents of equal marriage in Scotland are being urged to vote out Members of the Scottish Parliament who support the measure at the next election – in seats where they have small majorities.

Anti-equal marriage organisation Scotland for Marriage claim there are several constituencies where its list of supporters outnumbers the majority of the sitting MSP.

The group’s “highly sophisticated database” of 55,000 supporters and marginal constituencies has Scottish National Party MSP Bill Kid of Glasgow Anniesland as its chief target.

MSPs on the list who are targeted and support equality include Iain Gray, a former Scottish Labour leader and Duncan McNeil whose local constituency in Greenock contains 917 Scotland for Marriage supporters as opposed to his 511 majority.

A spokesperson for Scotland for Marriage said: “MSPs need to pay heed to what we are saying and our supporters will not be frightened to demonstrate their feelings at the next election. And for some, their votes could be decisive.”

However, Scotland’s Equality Network has dismissed Marriage for Scotland’s tactics as an “empty threat”.

Policy Coordinator Tom French said: “Introducing equal marriage is the right thing to do for a fairer and more equal Scotland, and with widespread public support it’s also a vote-winner.

“All the polls show that the large majority of people across Scotland believe it’s time LGBT people had full equality, including an equal right to marry the person they love.

“That’s why all the party leaders, and the overwhelming majority of MSPs from across the political parties, voted in favour of equal marriage.”

A Scottish Labour spokesperson added: “Our MSPs voted on the same sex marriage legislation based on what they believed was right.

“While we accept that this issue provokes strong reactions on both sides of the debate, we are confident that most people will recognise these decisions were taken after weighing up the evidence and listening to all of the arguments.”

In December, a poll by YouGov showed a majority of Scotland’s population support marriage rights for same-sex couples.

It was the first poll to be released since last month’s landmark vote on equal marriage by the Scottish Parliament.

56% of Scots support the legislation going through Holyrood; 35% are opposed, while 8% are unsure.

The Marriage and Civil Partnerships (Scotland) Bill passed its first Stage One vote on 20 November.

If the bill passes at Stage Two, the Stage Three vote is likely to happen around February.