Stormont would be given a say on new EU rules if the border backstop comes into force after Brexit, the government has proposed.
It comes as Prime Minister Theresa May continues in her bid to win over MPs opposed to her Brexit deal.
MPs are set to debate the withdrawal agreement ahead of a crucial vote in the House of Commons next week.
Cabinet Office Minister David Lidington told the BBC the plans amounted to giving the NI Assembly a “veto”.
However, his official written statement to Parliament does not contain the word “veto”.
The Democratic Unionist Party, who Mrs May relies on for her Commons majority, described the proposals as “meaningless” and of “no real significance”.
Sinn Féin said it was opposed to any Stormont “veto” mechanism.
Northern Ireland has been without a functioning devolved government since the executive collapsed in January 2017.
What is the government proposing?
The backstop is a position of last resort to maintain a soft border on the island of Ireland.
It would involve Northern Ireland staying in large parts of the EU single market, unless and until a long-term deal emerged that kept the border as open as it is now.
- Before the backstop would come into effect, the assembly would have to be consulted, with its views brought before Parliament ahead of a vote at Westminster
- The assembly would approve any new single market regulations for Northern Ireland introduced by the EU – updates to existing rules would automatically apply
- No divergence in rules applied in Northern Ireland and the rest of the UK
- Commitment to a role for the executive on the committees which would manage and oversee the backstop.
BBC News NI’s business editor John Campbell said the proposals appear to fall short of an outright veto as they do not specify that the assembly must give agreement before the UK government acts.
How have Northern Ireland’s parties reacted?
DUP MP Gavin Robinson said he did not think the proposals would lead to his party backing the withdrawal agreement.
“The withdrawal agreement says that even if there was disagreement in Stormont, even if Stormont decided that a proposal from the European Union wasn’t in the best interests of Northern Ireland, the UK government would legislate over our heads,” the Belfast East MP told BBC News NI.
“So in giving a consultative role, it doesn’t sound to me that the proposal that will be outlined is going to be the sort of comfort that people were seeking.”
“Anything that gives the DUP or extreme unionism any veto on progress in this society will be totally unacceptable,” Sinn Féin’s John O’Dowd said.
Mr O’Dowd added that the backstop was “as good as it gets”.
“I’m of the view that there are elements of the DUP who now want a no deal, who would be perfectly happy with all that a no deal brings with it and have linked themselves to the extreme right wing of the Tory party,” he said.
Ulster Unionist Party leader Robin Swann described the document as “insulting”.
“No amount of political assurances or explanatory notes will change the fact that there are fundamental problems with the backstop and the democratic deficit it will create,” he said.
The EU-UK agreement, known as the withdrawal agreement and signed in November, laid out the procedure for any new EU rules being introduced after the backstop is triggered.
The EU would inform the UK about the new rule and a joint EU-UK committee would discuss its implication for backstop within six weeks.
The committee either agrees to add the new rule to the backstop or if agreement isn’t reached will “examine all further possibilities to maintain the good functioning” the backstop.
If there is deadlock – no agreement “within a reasonable time” – the EU is entitled to “take appropriate remedial measures”.
The UK is now proposing that its position would be heavily influenced by the assembly.
Why have the proposals come forward now?
A vote on the draft withdrawal agreement is scheduled to take place in the House of Commons on Tuesday, after the original vote was cancelled on 11 December.
Mrs May relies on the support of the DUP’s 10 MPs and it is highly unlikely the withdrawal agreement will be approved by Parliament if they vote against it.
The DUP has repeatedly said it is opposed to the backstop and the withdrawal agreement is worse than a no-deal Brexit.
Mrs May has been seeking extra written assurances from European leaders to try and gain the support of the DUP and many Conservative MPs who oppose her deal.