Conservative Brexiters and the Democratic Unionist party would be unable to back a Northern Ireland deal that left any role for the European court of justice, a key backbencher has said, setting Rishi Sunak on an apparent collision course with his parliamentary party. With ministers saying Sunak was “on the cusp of a deal” to change post-Brexit arrangements in the region, Mark Francois, who chairs the influential European Research Group (ERG) of Tory MPs, warned of chaos if the prime minister tried to push through an unsatisfactory plan. He added that this would be “incredibly unwise” without a formal vote in the Commons, something to which the government has still refused to commit. With a deal expected to be announced as early as Monday, Sunak has begun the process of trying to sell his plan, using an interview with the Sunday Times to pledge that any proposals would “tick all of those boxes” in terms of concern from the DUP, the biggest unionist party. Dominic Raab, the justice secretary and deputy prime minister, said the government was “on the cusp of a deal” with the EU. “There’s real progress,” he told Sky’s Sophy Ridge on Sunday programme. “We want to make sure all the pieces are in place. But I think hopefully there will be good news in a matter of days, not weeks,” he said. While refusing to go into details, Raab effectively confirmed reports that the vital issue of how to deal with goods entering Northern Ireland from the rest of the UK would have an “intelligence-based approach” intended to minimise checks, with most items processed via a light-touch “green light” system. “Those are the kinds of things it’s been well known that we’ve been pushing for,” he said, adding that this would greatly reduce the oversight of the European court of justice (ECJ), which the DUP and ERG want removed altogether from Northern Ireland affairs. “If we can scale back some of the regulatory checks that apply and some of the paperwork that applies, that would in itself involve a significant, a substantial, scaling back for the role of ECJ,” Raab said. As part of this, any new rules that affected the EU’s single market – to which Northern Ireland is directly attached because of the lack of a trade border with the Republic of Ireland – would require a final say from the devolved assembly at Stormont. Speaking after Raab on the same programme, Francois said any role at all for the ECJ, however limited or curbed by oversight, would make the deal unacceptable. “Just putting in a couple of intermediate phases, with a situation where you still end up with the European court of justice, is effectively sophistry,” Francois said. “We’re not stupid. What we want is a situation where EU law is expunged from Northern Ireland so it is treated on the same basis as England, Scotland and Wales.” This would also not be acceptable to the DUP, he said, adding: “If the DUP don’t consent to the deal then it’s simply not going to fly.” While Raab reiterated Sunak’s refusal to confirm a formal vote on any new deal – “Inevitably, parliament will find a way to have its say,” he replied when asked about this – Francois insisted it was vital. “Given all the history of this, for the government to try and bludgeon this through the House of Commons without a vote of any kind would be incredibly unwise,” Francois said. The ERG chair criticised Sunak for holding back details of his plans, saying the prime minister needed to give his MPs plenty of time to consider the deal and not, as predicted, try to push it through within days. “If I were advising the prime minister, my honest advice to him would be: don’t try and bounce parliament next week, because that is likely to go badly wrong,” Francois said. “If they have got a deal they’re proud of, show us the text. Let us run it by our lawyers, let us fully understand what it means. And then at that point, we might be ready to vote on it.” If a vote did take place, Sunak could be guaranteed victory even with a significant Tory rebellion given Labour has pledged to vote in favour. This would, however, be politically very unpalatable for the prime minister. Also speaking on the Sky show, David Lammy, the shadow foreign secretary, said it would be vital for Labour to back Sunak on this. He said: “If he does get a deal then credit to him, because this is hugely important for the national interests of our country and for the people of Northern Ireland.”