In a letter to Donald Tusk, president of the European Council, the prime minister said that the backstop would jeopardise the Good Friday agreement and undermine Britain’s sovereignty. He called for it to be replaced with a commitment to “alternative arrangements” involving technological innovation to avoid a hard border between Northern Ireland and the Republic of Ireland. The demand, ahead of meetings Mr Johnson is to be holding with European leaders this week, increases concerns that Britain will leave the EU without a deal on October 31.