The king will host the EU chief, Ursula von der Leyen, after the signing of the final Northern Ireland protocol agreement with Rishi Sunak, prompting a furious reaction from the Democratic Unionist party and Tory Brexiters, who accused the prime minister of dragging the monarch into politics. The former DUP first minister Arlene Foster said she “cannot quite believe that No 10 would ask HM the king to become involved in the finalising of a deal as controversial as this one. It’s crass and will go down very badly in NI. We must remember this is not the king’s decision but the government, who it appears is tone deaf.” No 10 and the European Commission have said the meeting is not linked to the signing of the deal, an insistence that a number of MPs said stretched credulity. Several from across the political divide said it would be a grave mistake to involve the monarchy. The Labour MP Chris Bryant said it was a “terrible mistake from the government – we should never bring the monarchy into political disputes”. Charles will host tea for the European Commission president after she is expected to sign off on a Northern Ireland protocol agreement with Sunak. Buckingham Palace said in a statement – interpreted to place the onus on Sunak – that the king was acting on “the government’s advice” and that their discussions would feature a “range of topics”. Sammy Wilson, the DUP’s chief whip, was also deeply critical of the timing of the meeting, saying it risked “dragging the king into a hugely controversial political issue”. The former cabinet minister Jacob Rees-Mogg said the meeting called into question the king’s role when he had a duty to approve parliament’s legislation. “I think the sovereign should only be involved when things have been completed and accepted,” he told GB News. “The king gives assent to acts of parliament when parliament has agreed, he doesn’t express his view on acts of parliament when they are going through the process. I think the same applies – that His Majesty should not be involved until there is full support for this agreement.” A Buckingham Palace spokesperson said: “The king is pleased to meet any world leader if they are visiting Britain and it is the government’s advice that he should do so.” Downing Street defended the decision to advise the king to meet Von der Leyen, saying it was “not unusual”. The prime minister’s official spokesperson added: “He firmly believes it’s for the king to make those decisions. It’s not uncommon for His Majesty to accept invitations to meet certain leaders, he has met [the Polish] President [Andrzej] Duda and [Ukraine’s] President [Volodymyr] Zelenskiy recently. He is meeting with the president of the EU today.” No 10 played down suggestions that the royal audience could be seen as an endorsement by the palace of the Northern Ireland protocol deal. “We’d never seen to frame any action as an endorsement,” the spokesperson said. Asked why the final protocol talks were taking place in Windsor, he added: “There are a number of occasions when these sorts of talks have been held in significant places, this is no different.”