Boris Johnson has warned Remainers that as long as the EU believes Brexit could be stopped by parliament, the “less likely” he is to secure a divorce deal.
The prime minister has called for “everybody to be united” behind his aim of getting a withdrawal agreement before the deadline of 31 October.
Speaking to Sky News at 10 Downing Street, Mr Johnson said: “I’m afraid that the more our friends and partners think, at the back of their minds, that Brexit could be stopped – that the UK could be kept in by parliament – the less likely they are to give us the deal we need.”
The prime minister claimed his government’s decision to intensify no-deal Brexit preparations had “greatly strengthened” the UK’s position with the EU.
“They see that we’re serious,” he said.
Mr Johnson also predicted that if Brexit does not take place on 31 October, “it will do lasting damage to people’s trust in politics” and “lasting and catastrophic damage” to the Conservatives and Labour.
“This political generation won’t be forgiven for failing to honour that promise,” he added. “We told the people we would get it done. We have a way to get it done.
“We’re in the last stages now of negotiating with our friends about a way to get it done. If we can’t succeed in that negotiation, we must come out anyway.
“But the best way to succeed in that negotiation is for everybody to be united in the objective, for the UK’s negotiations to have the strongest possible hand.”
Mr Johnson – responding to the eruption of angry protests at his decision to suspend parliament for up to five weeks before the Brexit deadline – also insisted MPs would still have the opportunity to debate the UK’s exit from the EU before Halloween.
He said: “We’re coming up to the last period before we leave on 31 October and, in that period, parliament is going to have a lot of time – they’ve spent three years debating Brexit without actually getting it over the line – they’re going to have a lot of time for further consideration.”
The prime minister survived an immediate legal block on Friday against his decision to prorogue parliament from mid-September until 14 October.
The Court of Session in Edinburgh rejected a bid by a 70-strong group of MPs and peers to grant an emergency order against the suspension.
Judge Lord Doherty told the Scottish court: “I’m not satisfied that it has been demonstrated that there’s a need for an interim suspension or an interim interdict to be granted at this stage.”
However, he did bring forward a full hearing of the case to next Tuesday.
SNP MP Joanna Cherry, who is leading the legal action, challenged Mr Johnson to “swear on oath his reasons for the prorogation and submit himself to cross-examination if necessary”.
“The basis of our legal case is that it is unlawful to suspend parliament for the specific purpose of preventing parliament from scrutinising the Brexit process,” she said.
The judge’s decision means the government is likely to next week face two legal challenges against its prorogation of parliament, with former prime minister Sir John Major and Labour deputy leader Tom Watson joining a separate case initiated by anti-Brexit campaigner Gina Miller.
Mr Watson claimed legislation aimed at preventing a no-deal Brexit has also been drafted by a group of MPs, which they are likely to try and introduce in the House of Commons next week.
Foreign Secretary Dominic Raab had earlier defended the government’s suspension of parliament, suggesting it is required for Mr Johnson to push ahead with his domestic agenda.
“The idea that it is some kind of constitutional outrage is nonsense, it’s actually lawful, it’s perfectly proper, there is precedent for it,” Mr Raab said.
The foreign secretary spoke ahead of a 45-minute meeting with Ireland’s foreign minister Simon Coveney, who has accused the UK of offering “nothing credible” in terms of alternatives to the Irish border backstop.
Transport Secretary Grant Shapps told Sky News that Mr Coveney’s claims were “just not true”, adding: “We are putting forward ideas.”
He claimed “no self-respecting sovereign state could accept” the “anti-democratic” backstop – devised to prevent a hard border on the island of Ireland – due to its impact on Northern Ireland.
“Not all of the country would leave Europe at the same time and in the same way,” Mr Shapps said.