The DUP has warned the Government against intervening in Stormont affairs to pass Irish language laws at Westminster.
Party MP Sammy Wilson’s comments came after Sinn Fein called on Northern Ireland Secretary Brandon Lewis to take on responsibility for passing the legislation at Parliament.
Mary Lou McDonald made the request amid a stand-off on the language issue that potentially threatens the future of powersharing.
“Following the latest demand from Mary Lou McDonald, the Government must not interfere in devolved issues at the behest of Sinn Fein,” said Mr Wilson.
Former DUP leader Arlene Foster’s resignation as first minister on Monday set a seven-day clock running within which her successor, Lagan Valley MLA Paul Givan, must be appointed.
However, the joint nature of the office Mrs Foster shared with Sinn Fein deputy First Minister Michelle O’Neill, meant Ms O’Neill was automatically removed from her post when her partner in government quit.
She must also be renominated to her role within those seven days.
If one of the parties fails to renominate within the time period, a properly functioning executive cannot be formed and the UK Government assumes a legal responsibility to call a snap Assembly election.
Sinn Fein has made clear it will only engage in the renomination process if it was accompanied by the commencement of legislating for protections for Irish language speakers.
Irish language laws are an unfulfilled commitment within the 2020 deal that restored powersharing at Stormont.
New DUP leader Edwin Poots has vowed to implement all outstanding aspects of the New Decade, New Approach deal, including Irish language legislation.
However, he has declined to give Sinn Fein an assurance that he will move on the language laws in the current Assembly mandate, a key demand of the republican party, and had insisted there are other priorities the Executive should be focusing on, including the health service and economy.
On Tuesday, five Stormont parties, Alliance, the Green Party, People Before Profit, SDLP and Sinn Fein, signed a joint letter calling on the Executive and UK and Irish governments to agree a timetable to pass the legislation by the end of the mandate.
Following a meeting with Mr Lewis on Monday evening, Mrs McDonald said: “This evening we met with the British government and told them that they need to move the Irish language legislation through Westminster.
“A number of weeks ago the British government offered to legislate for Acht Gaeilge (Irish Language Act) in this way.
“At that time we said our preference was that Irish language legislation would be delivered through the Assembly and Executive as was agreed in New Decade New Approach.
“We have pursued that option vigorously over the last number of weeks.
“We have engaged intensively with the DUP and with party leader Edwin Poots.
“He has told us that they will not be delivering Acht in this mandate.
“This legislation was negotiated a year and a half ago and it is now incumbent on the British and Irish governments to act.
“This is the only way forward to finally resolve this issue.”
On Tuesday, East Antrim MP Mr Wilson warned against the move.
He noted the Westminster interventions in Stormont laws, including on abortion, during the three-year power-sharing impasse between 2017 and 2020.
“The Government foisted the most liberal abortion laws in the British Isles on Northern Ireland.
“Such actions only served to undermine devolution,” he said.
“To force through the latest Sinn Fein wish list will cause further damage to the credibility of the Northern Ireland Assembly.
“Repeated interventions in devolved matters undermines the manifesto promises of Northern Ireland parties and rightly raises questions about the confidence that voters can have in those they elect if their promises can be causally overridden by the Secretary of State.
“Rather than running to HMG when they can’t get their way, republicans should respect our mandate.
“Sinn Fein is playing the politics of ransom and are placing culture above health, education and economic recovery.”