Northern Ireland’s Alliance Party is to require all its candidates for the 2016 Assembly elections to openly back same-sex marriage.

Setting out its stall for the forthcoming elections, the party said it would make legislating for gay marriage part of its manifesto for the first time, and will require party members to “adhere to it”.

Despite the North’s rejection of same-sex marriage no less than three times after debates in the Stormont Assembly in recent years, the Alliance Party has noted the success of the same-sex marriage referendum in the Republic in formulating its new stance.

Interviewed by the BBC, the party’s MLA for Lagan Valley, Trevor Lunn, who previously opposed same-sex marriage – though he abstained in the latest vote – said he has now decided “to fall into line” on the issue. He acknowledged that, in addition to lobbying by gay advocates, the vote in the Republic, which he described as “impressive” had changed his mind.

“I will therefore support the proposal when it inevitably comes before the Assembly during the next term,” he said.

Reporting on the party’s announcement, The Belfast Telegraph said in its editorial that such a requirement placed on party candidates would amount to a form of discrimination.

“In a way, by saying that candidates must adopt an active pro-same-sex marriage line, the party could be discriminating against some of its own members by forcing them to do something that in their heart of hearts they disagree with”, the newspaper said.