By Joshua Nevett
BBC Politics
A group of Eurosceptic Tory MPs has branded a significant part of the prime minister’s new Brexit deal for Northern Ireland “practically useless”.
But the MPs have not decided whether to reject the deal in a key vote on Wednesday.
The European Research Group (ERG) has published a critical legal assessment on what the PM has agreed.
Downing Street has said there are no plans for substantial changes to the deal.
The deal – known as the Windsor Framework – was agreed by Prime Minister Rishi Sunak and the European Union (EU) last month to revise the Brexit deal for Northern Ireland.
The Democratic Unionist Party (DUP) has been refusing to take part in the devolved government in Northern Ireland until its concerns over post-Brexit trading arrangements are resolved.
Mr Sunak hailed his deal as a “decisive breakthrough” and many Conservative MPs, including those who supported Brexit, gave their backing to the agreement.
But his solution has now been heavily criticised by the two groups he wanted to win over the most, the ERG and the DUP, which is the biggest unionist party in Northern Ireland.
Mr Sunak has been under pressure to secure their backing and restore power-sharing in Northern Ireland in time for the 25th anniversary of the Good Friday Agreement in April.
US President Joe Biden is expected to visit Northern Ireland next month to mark the agreement, which ended decades of conflict on the island.
The ERG’s legal analysis may embolden Brexit-backing Conservative MPs to rebel against the government in Wednesday’s vote on the Stormont brake aspect of the deal.
The Stormont brake mechanism aims to give the Northern Ireland Assembly a greater say on how EU laws apply to Northern Ireland.
The DUP has already said it will vote against the government’s Brexit plans this week. But the government is still expected to win the vote with the support of Labour, who have backed the deal.
The Windsor Framework replaces the Northern Ireland Protocol, which led to disagreements between the UK and EU over trade rules.
Mr Sunak said the Stormont brake was proof that the UK had “taken back control” in the agreement he struck with the EU last month.
But legal experts have advised the ERG that EU law will “still be supreme” in Northern Ireland under the deal.
The analysis is based on the verdict of a so-called “star chamber” of lawyers hired by the ERG to pore over the details of the deal.
Even though the lawyers advised the ERG that the Stormont brake was “practically useless”, the group has declined to say whether they will vote against Mr Sunak’s deal or not.
ERG chairman Mark Francois told journalists that the “group hasn’t taken the decision yet” and it would be “down to individuals”.
Meanwhile, in Brussels, EU member states have approved key parts of the Windsor Framework.
They handed the European Commission – the EU’s executive – a mandate to bring forward the relevant changes on customs, VAT and the Stormont brake.
The EU-UK body which oversees the Northern Ireland Brexit deal is due to meet on Friday to formally ratify the legal changes.
The EU will have been anticipating the intervention of the ERG, which had a major influence on UK government policy during Brexit negotiations.
The group’s influence has waned since former PM Boris Johnson won a landslide election victory in 2019, promising to “get Brexit done”.
Since Mr Sunak took office last year, he has been seeking to end years of Conservative Party in-fighting over Brexit and its impact on Northern Ireland.
A major sticking point has been the trading arrangements agreed by the EU and Mr Johnson under his Brexit deal.
He negotiated the Northern Ireland Protocol to prevent a hard border between the Republic of Ireland and Northern Ireland.
The DUP has blocked the functioning of the power-sharing government at Stormont for more than a year in protest at the protocol.
The Windsor Framework was signed to alter the protocol – and aims to significantly reduce the number of checks on any goods arriving in Northern Ireland from Great Britain.
But DUP leader Sir Jeffrey Donaldson said his party had “unanimously agreed” to vote against it because of “ongoing concerns”.
He said the party would continue to assess the deal, but that “we don’t believe that this represents the significant progress that we need to see in order to have the institutions restored at this point”.