SINN Féin, the SDLP and the Alliance have backed a letter calling on the Executive to agree a timetable for the introduction of Irish language legislation, as Stormont hangs in the balance.
The cross-party letter from Conradh na Gaelige, also signed by the Greens and People Before Profit, said the Executive must stick to commitments agreed in last year's New Decade New Approach agreement.
The letter aims to put more pressure on the DUP not to renege on the agreement.
A row between the biggest unionist party and Sinn Féin on language legislation could derail the powersharing institutions after Arlene Foster stood down as first minister yesterday.
DUP leader Edwin Poots has said he will support Irish language legislation, but not necessarily before the next assembly election.
Sinn Féin has suggested it may not support the DUP's Paul Givan as first minister unless legislation is approved by ministers before July 10.
If no first minister is agreed within a week then a snap election is likely. If the executive falls, key decisions around lockdown measures and lengthy hospital waiting lists cannot be taken until after an election.
The letter, addressed to the Executive and the British and Irish governments, stated that an Irish language act must be introduced in this assembly mandate.
"The New Decade New Approach agreement contained a time-focused commitment that the language legislation would be implemented within 100 days," the letter read.
"Due to the pandemic, we can all appreciate the reasons for the initial deadline being missed.
"The legislation, however, is now ready to go and simply awaiting the political green light to proceed."
Sinn Féin Vice President Michelle O’Neill; SDLP leader Colum Eastwood; Alliance leader Naomi Long; Gerry Carroll of People Before Profit and Green Party leader Clare Bailey have all signed the letter.
"Any attempt to renege on agreed Irish language legislation, or indeed frustrate its progress, must be resisted," the letter read.
"If this legislation is not passed within the current mandate, much of the progress we have made in recent years may be undone.
"We also call on the British and Irish Governments to intensify their efforts in their roles as co-guarantors and indeed co-authors of the New Decade New Approach Agreement to facilitate all-party agreement on a timeline for implementation of this legislation within the current mandate.
"The timely passage of this legislation into law will herald an historic moment for the Irish language community."
Sinn Féin has previously accused Mr Poots of acting in bad faith over language legislation.
A party spokesman said: "We do not believe they will deliver on the Irish Language Act."
"Our position is that the nomination for first minister and deputy first minister has to be accompanied by legislation on the Irish language."
Last week, Conradh na Gaelige was granted leave by the High Court in Belfast to apply for a judicial review into the Executive's failure to implement a strategy for the Irish language.
