Rishi Sunak is preparing to face down his Brexit critics and press ahead with a deal on the Northern Ireland protocol if he can secure one in the coming days, government sources have said. The prime minister was said to be “relaxed” about a growing backlash over what hardline Eurosceptic MPs fear will amount to little more than a “glossary” on “how to implement” the existing protocol. Ahead of a video call with the foreign secretary, James Cleverly, the European Commission vice-president, Maroš Šefčovič, told reporters on Tuesday a deal was within grasp, and would be one negotiators hoped could “create conditions” for another 25 years of peace. “We clearly can see the finishing line, but in such a negotiation, being close doesn’t mean being done,” he said. The continuing confidence a deal can be done came as Eurosceptic MPs in the European Research Group of the Conservative party met the Democratic Unionist party leader, Sir Jeffrey Donaldson. They are demanding to see the full text of any deal on the Northern Ireland protocol, piling pressure on Sunak to meet their demand for radical changes to the Brexit trading arrangements, including eliminating EU law in Northern Ireland. This is seen as a non-starter for negotiators as it is the bedrock of the protocol and the means of avoiding a border on the island of Ireland. One senior ERG member said the “protocol doesn’t work, it will never work”. Another said it was vital Northern Ireland was freed from EU law, with 500 pieces of legislation applying in the region and not the rest of the UK since Brexit. “In reality, if all they are talking about is tinkering around the edges, it’s the same deal; it’s the status quo with a bit of a glossary explaining how to implement the protocol,” the MP said. Mark Francois, a leading member of the ERG said “We’d all like to solve this once and for all. But any MP worth their salt, if they’re asked to vote on a deal, wants to see it first. That’s not unreasonable. So that will mean … a legal text. So we too would be keen to read the legal text.” Other Tory MPs, however, believe the deal would be accepted without fuss by the majority of backbenchers, particularly if it had the backing of the former leading ERG members Chris Heaton-Harris and Steve Baker. They said most Tory MPs just wanted the Brexit deal done, rather than more internal infighting. “I don’t think the party has a complete death wish,” one said. “What is the ERG actually going to do about it? They might huff and puff, but there doesn’t have to be a vote and there’s no legislative vehicle to bring the deal down. Most MPs just don’t want this battle. We want to get on with other things.” After meeting with the ERG on Tuesday, Donaldson told reporters: “We recognise that progress has been made. There is still some way to go. There are still some very key issues that need to be resolved. “We will work with the government to make sure that we get the right outcome – an outcome that respects Northern Ireland’s place within the United Kingdom and its internal market.” The wrong deal, however, “will not restore powersharing but will cement division for future generations”. Getting a deal with Brussels over the line – and selling it to the party and the DUP – is the government’s primary focus amid concerns the process could lose momentum if the timetable slips beyond this week. “Everybody is on this full time,” one senior Tory said. Government insiders and EU sources indicated that if a deal was done, “things will move fast”, with a possible visit to London by the European Commission president, Ursula von der Leyen, within the week. There is concern that the longer the two sides leave it to strike a deal, the greater the risk of it unravelling. Friday has been ruled out, as it is the first anniversary of Russia’s invasion of Ukraine and Cleverly will be at the UN general assembly – which leaves Thursday, the weekend, or early next week as possibilities. “The window of opportunity here is narrow. From a substance point of view it is almost done but the final mile is most difficult,” said one EU source. While some ERG and DUP MPs are framing their concerns around a resumption of the Stormont assembly, government sources said the DUP never said yes to anything in advance. A source close to Downing Street said the text of the deal had been shared with the DUP last week, refuting claims that the party had not been consulted before the announcement. One Eurosceptic MP dismissed this, however, saying it had been a “command paper narrative” rather than a legal text.