The ball is in the UK government’s court with regards to actions which would see the restoration of the Stormont powersharing arrangements, DUP leader Sir Jeffrey Donaldson has said.
Mr Donaldson said there had so far been a “lack of meaningful action” from Westminster in addressing his concerns over post-Brexit trading arrangements.
It comes as Britain's Northern Ireland secretary Chris Heaton-Harris is holding a fresh round of talks with party leaders this week in a bid to break the Stormont stalemate.
The Assembly has been in flux for more than a year amid DUP protest action over the Northern Ireland Protocol.
The Windsor Framework was agreed by the EU and UK earlier this year as a way to reduce red tape on trade between GB and NI.
But the DUP has insisted it will not return to Stormont until the UK government provides further legislative assurances around Northern Ireland’s place within the UK internal market.
Senior civil servants have been left running Stormont departments and face having to make substantial cuts following a budget set by Mr Heaton-Harris.
Mr Donaldson and DUP deputy leader Gavin Robinson met Mr Heaton-Harris at Westminster on Wednesday.
Mr Heaton-Harris also met separately with SDLP leader Colum Eastwood.
Speaking after his meeting, Mr Donaldson said he urged Mr Heaton-Harris to recognise that there is “no solid basis for an Executive and Assembly until we have arrangements that safeguard in law NI’s place in the UK internal market and our constitutional arrangements are respected”.
He added: “The ball is in the government’s court.
“The DUP has a mandate to restore the Northern Ireland Assembly on a basis that unionists as well as nationalists can support.
“Consensus is the only way forward in Northern Ireland.
“Unionists just want a fair deal.
“Nationalists would never have been asked to accept the kind of arrangements north-south that unionists are being asked to accept between one part of the UK and another.”
The DUP leader added: “The government committed to taking action to restore our place in the UK internal market but whilst statements and headlines have been in plentiful supply, there has been a lack of meaningful action.
“We need stable and sustainable devolved government and we need funding for our public services that meet the needs of our people.
“Northern Ireland is a divided society.
“Quick fixes without solid foundations will do a disservice to those trying to make the NI Assembly work.”
Mr Eastwood said there can be “no summer recess on efforts to restore devolution”.
He added: “I have again outlined to the Secretary of State that the SDLP will play a constructive role in opposition to re-establish devolved government.
“People are quickly running out of patience with the glacial pace of progress on these issues.
“A summer of drift cannot be allowed to happen.”
Mr Heaton-Harris will hold further bilateral meetings with other party leaders over coming days.
He is expected to press the parties on their plans for a costed programme for government for any incoming executive.
It is understood that Mr Heaton-Harris has also received the first batch of replies from civil servants examining potential revenue-raising options for Northern Ireland.
Last month, the Northern Ireland Secretary wrote to Stormont permanent secretaries seeking more information about “measures that could otherwise improve the sustainability of public finances in Northern Ireland”.
These included introducing domestic water charges and drug prescription charges, and raising tuition fees.
Officials at the Northern Ireland Office are expected to meet the head of the Northern Ireland Civil Service in the near future to discuss the responses.
