The DUP wants a rethink of the controversial 'bedroom tax' as part of its price for supporting the next Westminster government.
The demand emerged as Secretary of State Theresa Villiers hosted talks aimed at resolving the crisis caused by Sinn Fein's withdrawal of support for welfare reform legislation.
The talks broke up without any breakthrough last night but the parties agreed to reconvene.
As the discussions began, Deputy First Minister Martin McGuinness accused London of being "a huge part of the problem".
"They are, by their agenda, effectively crucifying this Executive and making life very difficult for us to resolve these problems," he said.
His attack came after Mrs Villiers described Sinn Fein's withdrawal of support as a "setback" which could mean that Stormont's Budget becomes "unsustainable".
The US government urged the political leaders to resolve their differences before St Patrick's Day on Tuesday, which Northern Ireland's leaders usually celebrate in Washington. However, First Minister Peter Robinson has said he could see no point in going ahead with a White House visit in the absence of agreement.
US Special Envoy to Northern Ireland Gary Hart said his government urged all parties to "reach an understanding on the scope of the agreement as it applies to welfare payments to citizens of Northern Ireland, so that a successful series of meetings planned for St Patrick's Day can go forward as planned in Washington."
Meanwhile, DUP deputy leader Nigel Dodds warned the so-called under-occupancy tax - already amended for Northern Ireland in negotiations with the Government two years ago - had "inhumane and ineffective consequences".
His comments were seen as evidence that the DUP is prepared to back Labour after the May 7 election since leader Ed Miliband has already said his party will abolish the tax. With a hung parliament a real possibility, the comments from the fourth largest party at Westminster will be taken seriously.
Mr Dodds said: "We think Westminster can learn from what we did at Stormont over the bedroom tax. Despite the need - agreed across the political spectrum - to reduce public expenditure, we were determined that this failed policy should not be extended to Northern Ireland.
"It is time in the next parliament that the inhumane and ineffective consequences of the bedroom tax are revisited in the rest of the UK."
Apart from the bedroom tax, Mr Dodds cited defence expenditure and the protection of borders as on the DUP's priority list.
Story so far
The latest Stormont row centres on schemes to help benefits claimants under a reformed welfare system. Sinn Fein says they should cover future claimants, not just existing ones. It pulled support for the reforms, claiming the DUP had acted in bad faith by proposing to limit the schemes to current claimants. The DUP insisted there was never a deal to support future claimants and said that would require another £286m.