The DUP is set to back a Labour motion which could force the Government to publish the legal advice it has received on Brexit, including on how it will deal with the issue of the backstop.
On Monday the party said it it would use the 'humble address' procedure - the same parliamentary tool used to push for the release of the Brexit impact assessments last year - to force the Government's hand in publishing legal advice from the Attorney General.
The issue will be raised by Labour during the opposition day motion on Tuesday.
In a statement on Monday the party said: "Labour will force a binding vote in the House of Commons demanding that the Government’s legal advice on the withdrawal agreement – including the Irish backstop – is published once any Brexit deal is ready to be put to Parliament...
“...Labour will demand that MPs are able to scrutinise the Attorney General’s legal advice on the withdrawal agreement, including any Irish backstop proposal, so they can understand precisely what has been agreed and what its implications are for the future."
In its statement, Labour said some Tory MPs and the DUP had also called for the motion to be backed.
On Tuesday, a spokeswoman for the DUP confirmed to the Belfast Telegraph the party's MPs intended to vote with Labour on the motion.
The party's leader in the House of Commons Nigel Dodds tweeted on Wednesday his party would be supporting the motion.
We will be voting today for the publication of the legal advice on Brexit and the backstop.— Nigel Dodds (@NigelDoddsDUP) November 13, 2018
Keir Starmer MP, Labour’s Shadow Brexit Secretary, said: “It’s simply untenable for the Government to put forward any Brexit deal to Parliament without providing the legal advice on what’s been agreed.
“At this critical stage, MPs can’t be kept in the dark nor can we risk Parliament being bounced into a decision without having all of the facts available."
This week has seen a ratcheting up of speculation on the shape a future post-Brexit deal between the EU and Britain will take.
On Tuesday afternoon the BBC was reporting there was "optimism" following a Cabinet meeting, after earlier reports Theresa May was facing push back to her plans from Brexiteer members of her own Cabinet.
The vote on the Labour motion will take place on Tuesday afternoon.