An intervention by Boris Johnson in the row over solving the post-Brexit deadlock in Northern Ireland is “not entirely unhelpful”, a cabinet minister has said, as work to clinch a deal with the EU goes down to the wire. Penny Mordaunt, the Commons leader, suggested concerns reportedly raised by the former prime minister were a welcome reminder to Brussels of the threat that Britain could try to unilaterally override the Northern Ireland protocol. The bill designed to do so is paused, but Mordaunt said that “Boris is being Boris” and added: “The intervention by a source close to the previous prime minister is helpful to remind the EU of that bill”. Conservative MPs are quietly considering details about an agreement being worked up between the UK and EU to help ease trade barriers between Great Britain and Northern Ireland and reduce the jurisdiction of the European court of justice. Ahead of a crunch week for Rishi Sunak, the prime minister returned home from meeting EU leaders at the Munich security conference on Saturday and is spending Sunday in No 10 holding a series of informal meetings. Downing Street hoped to be able to announce a deal for overhauling the way the protocol works on Monday, but buy-in from the Democratic Unionist party (DUP) is viewed as key. A group of hardline Brexiters in the Tory party – known as the European Research Group – has also said it will remain in “lockstep” with the DUP, dangling the threat of a mass rebellion over Sunak. Johnson has become concerned that a successful deal will lead to the government ditching the Northern Ireland protocol bill, allowing the UK to unilaterally rip up some Brexit arrangements in the region, the Observer revealed. The Sunday Times also quoted a friend of Johnson’s as saying: “His basic worry is that we took the powers in the bill and we are not using them, and we haven’t got as good a deal as we would have because we didn’t stick with it.” Though some government insiders are frustrated given they feel Johnson is being a thorn in their side at a key stage in negotiations, Mordaunt said his purported interventions were “not entirely unhelpful”. She suggested reminding Brussels of the bill was helpful leverage, telling the Sunday with Laura Kuenssberg show: “The EU is talking about things it previously said it wouldn’t talk about.” Ensuring the support of the DUP for any deal is paramount, Mordaunt insisted. “Unless we have every community in NI behind this deal, it won’t last, it won’t work,” she told Sky’s Sophy Ridge on Sunday programme. Given the DUP has refused to re-enter power-sharing, leaving Northern Ireland without an executive for a year, citing concerns with the protocol, Mordaunt admitted that a “key part” of any deal would be “getting the assembly stood up again”. She dismissed the potential for any rebellion by Tory MPs, saying “that is irrelevant unless it works for the whole of Northern Ireland”. Downing Street has not yet decided whether to hold a vote on any deal, Mordaunt added. However, Wendy Morton, the former chief whip under Liz Truss, urged ministers to keep all backbenchers on side. “We have to have something that works and that takes all our communities and our party with us,” she told the BBC. Labour repeated its offer to provide political cover to Sunak by supporting any deal agreed with the EU, meaning the prime minister would easily be able to win any vote on it regardless of a rebellion in his own party. Yvette Cooper, the shadow home secretary, said she hoped a deal was imminent as one was “strongly needed”.