The British government has again told parties in the Stormont Executive that it intends to introduce an Irish language act for Northern Ireland and invited them to a technical briefing on the proposals.

A letter sent to the parties this morning says the legislation will be introduced "as soon as parliamentary time allows".

It says: "The UK Government is now taking forward the balanced package of identity, language and culture legislation that was carefully negotiated in the New Decade, New Approach agreement, as the Northern Ireland Executive has not done so."

Northern Secretary Brandon Lewis said in June that the process to introduce the legislation would be initiated this month, but that deadline has now been missed.

That promise was the basis for Sinn Féin agreeing to go back into power sharing with the DUP following the resignation of Arlene Foster as First Minister.

The invite to the technical briefing by officials from the Northern Ireland Office was issued the day after DUP leader Jeffrey Donaldson said his party had warned the British government not to legislate on language until the dispute over the Brexit protocol is resolved.

The Lagan Valley MP has warned that his party will collapse the Stormont Assembly if the issue is not resolved to its satisfaction.

Senior DUP sources say a unilateral move on the Irish language before the protocol negotiations conclude would be unacceptable and could make the party's participation in Stormont Executive untenable.

Mr Donaldson told RTÉ News yesterday: "I don't think the government should allow themselves to be distracted by other issues. Frankly, I've just come from a business that has been harmed by the protocol, whose trading arrangements with Great Britain are being undermined on a daily basis.

"That matters to people, it's about their jobs, it’s about their future, and that matters a lot more than issues around culture. So, I think we need to get our priorities right here and that means resolving the issues around the protocol."

But Sinn Féin’s leader in Northern Ireland and Stormont’s Deputy First Minister Michelle O’Neill yesterday said the Irish language Act and the Brexit protocol are two distinctly different issues and that her party expects Brandon Lewis to deliver on his commitment.

"I expect them to deliver that now, none of us can be held to ransom by the DUP," she said.

"I'm not working on the basis of failure. I’m work on the basis that there will be an Irish language act, that the that legislation will be published in the coming weeks, and I will hold the British government to that."

The letter sent to be parties this morning asks them to confirm their interest in the briefing and the identities of representatives they want to attend. No date has yet been set.