Rishi Sunak’s plan to get a deal on the Northern Ireland protocol over the line this week has suffered a setback as further talks with Brussels failed to reach agreement and frustration among his Conservative allies with hardline Brexiters bubbled over. Despite a concerted effort to get the deal done, senior government sources now believe it is unlikely to be struck until next week at the earliest, amid concerns that a loss of momentum could increase the chance of it unravelling altogether. Some Conservative MPs, including close allies of Sunak, are anxious that he has missed his best opportunity to reach an agreement, since Friday has been ruled out because it clashes with the first anniversary of Russia’s invasion of Ukraine, which is expected to dominate the weekend. The prime minister held overnight talks on Tuesday with the president of the European Commission, Ursula von der Leyen, fuelling fresh speculation that the UK is nearing agreement with the EU over the protocol. It was the second time in five days that Sunak and Von der Leyen had spoken. However, there are no ministerial discussions planned for Thursday, and the Brussels chief is supposed to be in Italy, suggesting it is unlikely she will travel to London. Government sources have said Sunak is preparing to defy his Tory MP critics in the European Research Group (ERG) and press ahead with the deal if he can secure one within the coming days. He is coming under growing pressure from moderate Conservatives to ignore the hardline Brexiter wing of the party. One Whitehall source said Downing Street had “priced in the reaction from the ERG and the Democratic Unionist party [DUP]”, and that the recent backlash did not weaken their resolve to get a deal. In an interview with GB News on Wednesday, Suella Braverman said she will not “support selling out on Northern Ireland and allowing the EU a foothold in the United Kingdom”. The home secretary added: “It’s absolutely vital we safeguard what we’ve gained from the Brexit vote, that we go forward as a United Kingdom where the integrity of our union is safeguarded and we properly take back control. I know the prime minister shares that objective.” James Cleverly, the foreign secretary, was quizzed about the possible deal at a pre-arranged meeting of the 1922 Committee of Tory backbenchers, which drew a sparse gathering of fewer than 20 MPs. As they left, attenders said he gave no new details. One senior backbencher, Gloucester MP Richard Graham, called on more hardline colleagues to not obsess about “every individual comma or sub-clause” in a possible deal with the EU, and instead focus on what was best for people in Northern Ireland, including a functioning devolved assembly. “Colleagues here will naturally tend to worry about the detail and the purity of the arrangements being made, because we don’t know what the detail is,” he said. “I understand the concerns, but we have to bear in mind what the ultimate goal is, and the fact there are a lot of hazards still in the way.” Another senior Conservative said: “Rishi will get the deal done but he needs to crack on and ignore the ERG.” A third MP added: “He can’t afford for it to slip too far into the long grass and lose momentum.” Despite some critics drawing comparisons with Theresa May’s handling of Brexit, Sunak is said to be determined to get a deal over the line to help restore relations with the EU, show he has a grip on his party, and help neutralise Brexit as an issue at the next election – the Tories having won the last one by promising to get it done. However, some ministers are concerned that the longer he takes to confirm that a deal is in the bag, the more likely the details are to be selectively leaked by those intent on causing mischief. Downing Street has said that a final deal has not yet been agreed, but some believe the substance is there and the main outstanding issue in talks between Cleverly and Maroš Šefčovič, the European Commission’s vice-president, is the language that should be used to describe it. Sunak told MPs the deal would meet the demands of the DUP – which wants radical changes to ensure that the region has a role in making the EU rules that apply to trade as part of the Brexit arrangements – but refused to say if it would involve reopening the wider withdrawal agreement. The DUP leader, Sir Jeffrey Donaldson, had told the prime minister that tinkering around the edges of the protocol would not amount to a fresh start on Brexit. “Will he agree with me that it is unacceptable that EU laws are imposed on Northern Ireland with no democratic scrutiny or consent?” he asked. “Will he assure me that he will address these fundamental constitutional issues and do so not just by tweaking the protocol, but by rewriting the legally binding treaty text?” Sunak also declined to confirm whether MPs would have a vote on any deal, during prime minister’s questions. “Of course parliament will express a view,” he told Keir Starmer, when asked by the Labour leader, who then said he would take that as a confirmation. However, his press secretary then told reporters: “We’re not going to get ahead of ourselves, talks are ongoing, we don’t yet have a deal. There is nothing to vote on yet, we don’t have a deal.” Earlier on Wednesday, Sunak held a meeting with business leaders in Northern Ireland who reported an impressive command of the detail of their asks on customs, VAT, state aid, tariff reimbursement and consumer parcels. “It was very clear that the prime minister was not only fully engaged but had an intimate understanding of the issues and the need to strike the balance between protecting consumers and the market access our exporters depend upon,” said one who was on the call. They said solutions on trade friction had moved quickly. “In the last 24 hours, it appears many issues we have flagged could be resolved including ensuring goods available to consumers in Southampton are available in Strabane.”