Keir Starmer has accused Rishi Sunak of being too weak to take on Brexit “malcontents” on the Conservative benches and reach a deal with the EU over Northern Ireland, as the pair tussled over Brexit at prime minister’s questions. In a rare airing of the issue at the event, Starmer reiterated Labour’s pledge to “put country before party” and help Sunak push a deal through parliament, even if hardline Brexiter Tories rebelled. “He should accept our offer, and ignore the howls of indignation from those on his side who will never take yes for an answer. Why doesn’t he just get on with it?” the Labour leader asked. “It’s the same old story. The country has to wait while he plucks up the courage to take on the malcontents, the reckless, the wreckers on his own benches.” Sunak, who had hoped to present a revised deal on post-Brexit trading arrangements this week – a timetable that could slip amid disquiet from the Democratic Unionist party and some Tories – used his answers to try to reassure these groups of his intentions. “He should know that I am a Conservative, a Brexiter and a unionist, and any agreement that we reach needs to tick all three boxes,” he said. Asked by Starmer to confirm that parliament would get a vote on a changed deal, which is not mandatory, Sunak equivocated, saying: “Of course, parliament will express its view.” The prime minister declined to give any details of the possible deal when questioned about how it would square the irreconcilable necessities of not imposing a border between Northern Ireland and the Republic of Ireland, while also not requiring checks between Great Britain and Northern Ireland and some EU oversight. Starmer began by noting that Boris Johnson, whose Northern Irish protocol Sunak is seeking to amend, had falsely promised there would be no trade barriers in the Irish Sea. “His predecessor told businesses that there would be no forms, no checks, no barriers of any kind,” Starmer said. “That was absolute nonsense and it destroyed trust. So, in the interests of restoring that trust, will he confirm that to avoid a hard border on the island of Ireland, the deal he’s negotiating is going to see Northern Ireland continue to follow some EU laws?” After Sunak said Starmer was “jumping ahead”, the Labour leader accused him of being too weak to level with Tory backbenchers, adding: “At some point the irreconcilables on his benches are going to twig, and they’re going to come after him.” In response, Sunak raised Starmer’s former support for remain, and for a second referendum on Brexit. “It’s his usual position when it comes to the European Union – it’s give the EU a blank cheque and agree to anything they offer. It’s not a strategy, that’s surrender,” he said. As Conservative MPs cheered, Starmer replied: “The sound you hear is them cheering the prime minister pulling the wool over their eyes.”