THE Scottish Government has published a letter it received from Arlene Foster asking it to exclude Northern Ireland couples from conversion laws surrounding gay marriage.
The correspondence, signed by the DUP leader, was sent in 2015 when she was finance minister.
It follows calls to publish the letter when its existence emerged after the Westminster election results sparked fresh criticism of the DUP's opposition to gay marriage.
Gay rights campaigners said they were "stunned" by the letter and called on Mrs Foster to explain her actions.
Last week Mrs Foster had denied sending a letter after former Scottish minister Marco Biagi claimed she asked him to curtail same-sex marriage access for Northern Ireland couples.
"I'm not quite sure what he was referring to but it certainly wasn't a letter from me and I have no recollection of a letter from me," she told BBC Radio Ulster's Inside Politics programme.
"If I had written to him officially as minister of finance or something like that around recognition laws here in Northern Ireland, I have no recollection of it. I certainly didn't write in a personal capacity."
In her letter to Mr Biagi, Mrs Foster said she was "concerned" about a legislative change to allow civil partnerships registered outside Scotland to be converted to Scottish civil marriages.
The DUP leader added that "neither of us would wish to place same-sex couples in an uncertain legal position".
"In this instance, we can achieve legal certainty by restricting the definition of a 'qualifying civil partnership' so as to exclude civil partnerships which were entered into in Northern Ireland," she said.
Writing in response, Mr Biagi said he had considered the issues but concluded that it would "not be appropriate to exclude civil partnerships registered in Northern Ireland from the Order".
The Scottish Government also released a letter about the same matter from the DUP's Simon Hamilton written in March 2015 when he was finance minister.
Rainbow Project director John O'Doherty called for Mrs Foster to explain her letter.
"Arlene Foster owes the people of Northern Ireland an explanation and apology for covertly seeking to limit their rights and a further apology for maintaining that she had not taken this course of action," he said.
Solicitor Ciaran Moynagh – who is assisting in a legal challenge by a same-sex couple seeking to have their marriage in London recognised in Northern Ireland – expressed shock at the correspondence.
"I was stunned to see in black and white the attempts by DUP ministers to further limit the rights of NI same-sex couples," he said.
"The letters clearly demonstrate how the DUP try to use whatever political influence they have to restrict LGBT+ rights.
"This is of obvious and pressing concern given the current 'confidence and supply' negotiations with Downing Street."
Alliance leader Naomi Long hit out at Mrs Foster failing to recall the letter, saying: "It appears Arlene Foster was not across every 'jot and tittle' on this matter, as was the case with RHI."
Green Party MLA Clare Bailey branded it "clear hypocrisy", after the DUP previously criticised Scotland's First Minister Nicola Sturgeon for discussing whether women in Northern Ireland could access NHS abortions in Scotland.
Asked about the finance minister being involved in marriage issues, Stormont's finance department said it is responsible for some aspects of civil law.
