DUP leader Sir Jeffrey Donaldson has claimed the new agreement – which has won the backing of his unionist party – will involve “substantive” changes to trade arrangements.
Sir Jeffrey insisted it would remove all post-Brexit checks on goods moving into Northern Ireland from Great Britain under a deal to restore power-sharing at Stormont.
As well as claiming “zero checks, zero customs paperwork” on goods moving over the Irish Sea, the DUP chief also said Northern Ireland would no longer automatically have to follow EU laws.
Mr Sunak’s Northern Ireland’s secretary Chris Heaton-Harris said the changes were “significant” – but refused to be drawn on the details, and made clear they would not need any approval by the EU.
Mr Heaton-Harris said he would set out the full agreement with the DUP on Wednesday – and revealed that more than £3bn would be spent in Northern Ireland if the parties get back to Stormont.
The DUP, Sinn Fein and other Northern Ireland parties are due to meet later on Tuesday to discuss the next steps to get the executive back up and running after the unionists two-year blockade.
Mr Sunak and EU Commission president Ursula von der Leyen agree a new post-Brexit deal in February 2023 – the Windsor Framework – aimed at reducing checks on Irish Sea trade.
No 10 declined to confirm DUP leader Sir Jeffrey’s claim the new deal would result in “zero checks, zero customs paperwork” on goods moving within the UK.
But Mr Sunak’s official spokesman said it would not affect the PM’s Windsor Framework agreement with Brussels. “It will not change the powers and freedoms we agreed … in the Windsor Framework.”
Mr Heaton-Harris – asked if the Windsor deal would now have to be renegotiated – told broadcasters: “I don’t believe so.”
The Northern Ireland secretary said there were “some significant changes” and the new agreement had achieved “a vast array of decent improvements to make sure our internal market works properly”.
It is understood the Sunak government will introduce two statutory instruments at Westminster on Wednesday so parliament can sanction the DUP agreement – with possible changes to the Internal Market legislation, rather the Windsor deal with the EU.
Sir Jeffrey expressed hope that the Stormont institutions could be back up within days after he secured the backing of his party executive for proposals on Monday night.
The DUP leader told BBC Radio Ulster that the “new arrangements remove those restrictions” set out in the Northern Ireland Protocol, part of Boris Johnson’s Brexit deal.
“Zero checks, zero customs paperwork on goods moving within the United Kingdom,” Sir Jeffrey claimed. “That takes away the border within the UK between Northern Ireland and Great Britain, and that is something that’s very important.”
Sir Jeffrey announced his support for a Stormont return at post-1am press conference. He said there was “decisive” backing from the 130-strong party executive after a five-hour meeting on Monday night.
But support for the deal is not unanimous within the DUP – as several senior figures remain fiercely opposed to the proposed agreement to restore powersharing.
Around 50 loyalist and unionist protesters assembled outside Monday night’s meeting, many carrying posters and banners warning against a DUP “sellout”. Some shouted at DUP members as they drove into the grounds of the venue.