Former Health Minister Jim Wells has claimed he and other MLAs will split from the DUP if it agrees to Sinn Fein's demand for gay marriage.
While the DUP appears to be willing to negotiate on the Irish language, same-sex marriage is a 'red line' issue that will not be accepted by many members, Mr Wells said.
"Peter will not marry Paul in Northern Ireland," he vowed.
Mr Wells also said that the DUP will kill off Sinn Fein's proposal for a civil forum because a similar forum in the Republic led to a successful referendum on same-sex marriage.
"We will strangle that idea at birth if that's what it's going to bring. Nobody wants it except Gerry Adams anyway," he said.
Sinn Fein MLA Megan Fearon has said the DUP are out of touch with the people on the issue of marriage equality.
Megan Fearon said: "Comments from Jim Wells that the DUP could split if there is equal marriage in the north highlights the attitude of that party to equality. His remarks show just how out of touch he and his party are with the views of the general public.
"And it shows once again that the DUP is placing its party self interest above the need for equality for all.
"Marriage equality is an issue where the people are ahead of many politicians."
During his Easter Sunday 1916 commemoration speech, Mr Adams said that progressive parties that favour a civil forum should not fear another election if Sinn Fein-DUP talks do not succeed in setting up a new Executive.
The civil forum would allow ordinary people to put forward ideas for legislation, similar to the constitutional convention in the Republic that meets to recommend constitutional change.
In 2013, 79% of the Republic's convention delegates recommended the constitution be changed to allow same-sex marriage.
A referendum in the Republic approved same-sex marriage two years later.
Mr Wells said the DUP would vigorously oppose such a forum in Northern Ireland if same-sex marriage was discussed and would not allow Sinn Fein to bypass the Assembly.
Secretary of State James Brokenshire met the five main Assembly parties yesterday in an effort to get the Executive running again.
Asked if, as a compromise, the DUP would maintain its opposition to same-sex marriage but lift its veto against it in the Assembly, Mr Wells said that was tantamount to accepting gay marriage in Northern Ireland.
"Don't even think that. That's an absolute no," he added.
"Some of us would walk before that would happen. We feel very, very strongly about that."
The DUP has repeatedly used the petition of concern to block same-sex marriage legislation in the Assembly, even though it is favoured by a majority of MLAs at Stormont.
A petition of concern, which can veto any legislation, requires the signature of 30 Assembly members.
Until the March 2 election this year, the DUP's 38 MLAs were easily able to defeat same-sex marriage.
Now with 28 MLAs, the DUP lacks the numbers to single-handedly use the block if the Assembly is restarted.
However, ex-DUP stalwart and current TUV leader Jim Allister has indicated his willingness to support a veto, bringing the number up to 29.
Mr Wells and other DUP colleagues believe that a conservative member of the Ulster Unionists will bring the numbers up to 30.
While same-sex marriage remains an impassable power-sharing barrier between the DUP and Sinn Fein, former First Minister Arlene Foster has been offering an olive branch on Irish language issues, without committing to an Irish Language Act.
Mrs Foster said that she will meet non-politicised Irish language groups very soon.
The DUP has written to Pobal - the Irish language advocacy group - accepting a meeting before the general election on June 8.