GETTYThe DUP agreed a deal with the Tories
The party, which props up Theresa May’s government, could also vote against higher tuition fees during a further opposition day debate calling for this year's hike to be scrapped.
It would be the first time the unionists have broken with the Tories since they formed a confidence and supply arrangement with them after the election in a £1billion deal.
Ian Paisley confirmed to the Commons on Wednesday his party could support a Labour motion calling for an end to the public sector pay cap in the NHS and a “fair pay rise” for staff.
Speaking as MPs began the opposition day debate, he said: "I must say that myself and my colleagues are minded to support the motion.”
DUP MPs were among those to sign a similar early day motion earlier this year.
The DUP’s stance would leave the Government facing defeat on both issues, although Tory MPs are expected to abstain from the votes because they are non-binding.
DUP MP Jeffrey Donaldson told the Guardian that the votes would not affect his party’s relationship with the Tories.
He said: “We made clear to her majesty’s government on issues like this we reserve the right to vote on the basis of our own manifesto. This doesn’t threaten the deal at all.”
But Health Secretary Jeremy Hunt told the Commons that Labour’s motion was “bogus”.
He said: “The consequences of losing financial discipline for a government are not just pay freezes and one per cent caps, but a million unemployed as a result of that recession we had post 2008.”
The result of the votes will not be binding but is likely to increase pressure on the Prime Minister over public sector pay.
Earlier this week Downing Street said the seven-year public sector pay cap is to be scrapped, unveiling a 1.7 per cent hike for prison officers and improvements totalling 2 per cent in police pay for 2017/18.
But shadow health secretary Jon Ashworth said the Government must not play different areas of the public sector off against each other.
He said: "If the Government are indeed abandoning this cap, let us put them on notice.
"It must apply to the whole of the public sector, including the 55 per cent of workers who are not covered by the pay review bodies.
"And we also put them on warning, we will not accept a divide-and-rule approach, we will not accept playing one set of public sector workers off against another.”
Mr Ashworth also said it "wasn't good enough" for ministers to grant more flexibility over pay and expect hospitals to fund a pay increase for staff from existing budgets.