The DUP has said that “key issues of concern” remain over Rishi Sunak’s protocol deal, as Downing Street stressed that Stormont would get a say in the application of EU law under new changes.

Sir Jeffrey Donaldson’s party is poised to study details of the Windsor Framework, which remove trade barriers for Northern Ireland and creates a new “brake” for Stormont on EU laws, before giving its view on the UK-EU deal.

In a statement on Monday, the DUP leader said: “We welcome the publication of the outcome of the Government’s negotiations with the EU which ends a period of speculation and spin, often from those who know little about Northern Ireland.

“In broad terms, it is clear that significant progress has been secured across a number of areas – whilst also recognising there remain key issues of concern.

“There can be no disguising the fact that in some sectors of our economy, EU law remains applicable in Northern Ireland.”

The opinion of the DUP is seen as a key bellwether for the success of any deal, with the party’s backing crucial to restoring powersharing at Stormont.

Sir Jeffrey said that his party will now “study the detail” of the Windsor Framework, “as well as examining the detail of any and all underpinning legal texts”.

He added: “Where necessary we stand ready to engage with the Government in order to seek further clarification, re-working or change as required.

“Ultimately the party will now assess all these proposed outcomes and arrangements against our seven tests, outlined in our 2022 Assembly election manifesto, to determine whether what has been published meet our tests and whether it respects and restores Northern Ireland’s place within the United Kingdom.”

In the Commons later on Monday, Sir Jeffrey asked the Prime Minister: “The overwhelming majority of what we produce we sell within our own internal market.

“And I want an assurance from the Prime Minister that not just now but in the future, the Government of the United Kingdom will protect Northern Ireland’s place within that internal market and will not allow the application of EU law to put barriers in the way of our ability to trade with the rest of our own country.”

Earlier, Prime Minister Rishi Sunak said he understood parties in Northern Ireland would want to take time to assess the new deal.

“I also recognise that parties and communities across Northern Ireland will want to take the time to consider the detail of what we’re announcing today and we should give them the time and the space to do that, and I fully respect that,” he told reporters.

He repeated that message in his reply to the DUP leader.

Downing Street is hoping that among all the changes to the deal, a new arrangement dubbed the “Stormont brake” will help address unionist concerns about a lack of democratic input in Northern Ireland into the EU regulations that apply there.

Described in the agreement as giving Stormont a “genuine and powerful role” in deciding whether significant new rules on goods impacting life in the region will apply, it is expected to function along the same lines as the Good Friday Agreement safeguard of the petition of concern.

Under that Stormont arrangement, 30 MLA signatures are need to secure a valid petition, which then triggers a vote that requires a majority of both nationalist and unionist MLAs to pass.

It remains to be seen how the arrangement will be introduced into the Stormont institutions, if powersharing does return, but Downing Street has been clear that once triggered the brake will give the Government the power to veto any new or amended EU rule.

Former Brexit secretary David Davis predicted that the DUP could abstain if Parliament does hold a vote on the deal.

“I suspect they’ll end up abstaining rather than supporting, but even so I think that that will be massively important within our own party, there’ll be a lot of our colleagues who will look to the DUP and say, ‘what are they going to do? If they vote against, then I can’t support the Government,” he told Jacob Rees-Mogg’s new show on GB News.