Boris Johnson is refusing to sit down for talks with EU leaders until they agree to ditch the Irish backstop from the Brexit withdrawal agreement, despite invitations to meetings from the German chancellor, Angela Merkel, and the French president, Emmanuel Macron.

His official spokeswoman said the prime minister had made clear that he wanted to strike a deal, but that there was no point in holding face-to-face talks unless the EU agreed to reopen the agreement.

But on a visit to the Trident nuclear base at Faslane in Scotland on Monday, Johnson painted a more optimistic picture of the prospects for talks, telling reporters there was “ample scope” to achieve a new deal.

He said: “We are not aiming for a no-deal Brexit at all. What we want is to get a deal and I’ve had some interesting conversations with our European partners. I’ve talked to [the European commission president] Jean-Claude [Juncker] and Angela Merkel and we’re reaching out today to [the Irish prime minister] Leo Varadkar. The feeling is, yes there’s no change in their position, but it’s very, very positive.”

But he added: “They all know where we are: we can’t accept the backstop, it was thrown out three times, the withdrawal agreement as it stands is dead and everybody gets that. But there is ample scope to do a new deal and a better deal.”

Quick guide What is the Brexit ‘backstop’? Show Hide What is the original ‘backstop’ in the withdrawal agreement? Variously described as an insurance policy or safety net, the backstop is a device in the withdrawal agreement intended to ensure that there will not be a hard border between Northern Ireland and the Republic of Ireland, even if no formal deal can be reached on trade and security arrangements. It would mean that if there were no workable agreement on such matters, Northern Ireland would stay in the customs union and much of the single market, guaranteeing a friction-free border with the Republic. This would keep the Good Friday agreement intact. Both the UK and EU signed up to the basic idea in December 2017 as part of the initial Brexit deal, but there have been disagreements since on how it would work. The DUP have objected to it, as it potentially treats Northern Ireland differently from the rest of the UK, creating a customs divide in the Irish Sea, which is anathema to the unionist party. Hardline Tory Eurosceptics also object to it, as they perceive it to be a trap that could potentially lock the UK into the EU’s customs union permanently if the UK & EU cannot seal a free trade agreement. That would prevent the UK from doing its own free trade deals with nations outside the bloc. What was added to May’s withdrawal agreement? Joint interpretative instrument

A legal add-on to the withdrawal agreement was given to Theresa May in January 2019 to try to get her deal through the UK parliament. It gives legal force to a letter from Jean-Claude Juncker and Donald Tusk, the presidents of the commission and council. This stated the EU’s intention to negotiate an alternative to the backstop so it would not be triggered, or, if it was triggered, to get out of it as quickly as possible. Unilateral statement from the UK This set out the British position that, if the backstop were to become permanent and talks on an alternative were going nowhere, the UK believes it would be able to exit the arrangement. Additional language in political declaration This emphasises the urgency felt on both sides to negotiate an alternative to the backstop, and flesh out what a technological fix would look like. However, it failed to persuade the attorney general, Geoffrey Cox, who said that while it ‘reduces the risk’ of the UK being trapped in a backstop indefinitely, it does not remove it. What happens next? Boris Johnson declared the Northern Ireland backstop ‘dead’ during his leadership campaign, and promised to throw it out of any deal he renegotiated with the EU. The EU has repeatedly stated that it will not reopen the withdrawal agreement for renegotiation. Daniel Boffey, Martin Belam and Peter Walker

While Johnson has spoken to Merkel and Macron, there are no plans to accept their invitations to visit without a change in their position on the backstop. Irish officials are understood to view the delay in contacting Varadkar as indicative of an unwillingness to enter serious talks. Varadkar is adamant that the backstop must stay to prevent a return to a hard border on the island of Ireland and preserve the integrity of the single market.

Facebook Twitter Pinterest Boris Johnson arrives for a meeting with Nicola Sturgeon in Edinburgh on Monday. Photograph: Jeff J Mitchell/Getty Images

A Downing Street spokeswoman said: “The PM has been clear that he wants to meet EU leaders and negotiate, but not to sit down and be told that the EU cannot possibly reopen the withdrawal agreement. And that is the message that he has been giving to leaders when he has spoken to them on the telephone so far.

“The EU has said up to now it is not willing to renegotiate [the backstop] … The prime minister would be happy to sit down with leaders when that position changes. But he is making it clear to everybody he speaks to that that needs to happen.”

Asked about his plans to kickstart negotiations with the EU over the summer, after the foreign secretary, Dominic Raab, appeared to suggest on Monday morning that he would not reopen talks until the EU agreed to ditch the backstop, Johnson said: “I believe in reaching out. I’ve already been talking to colleagues around the table in Brussels, I have absolutely no inhibitions about that. We are going to engage and obviously ask for very profound changes to the current basis for leaving the EU.”

Although the formal position of the EU that there could be no further negotiations on the withdrawal agreement remained unchanged, he said, “they understand that the UK and the EU are two great political entities and it is possible for us to come up with a new deal that will be to the benefit of both sides”.

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Despite the positivity of Johnson’s outlook in Faslane, where he met naval personnel working inside the nuclear submarine HMS Victorious, his underlying position on talks makes clear that No 10 is proceeding towards a no-deal Brexit unless EU leaders change their minds about not reopening the withdrawal agreement. It is counter to expectations among some of Johnson’s supporters that he would embark on a whistle-stop diplomatic tour of European capitals to propose an alternative to the backstop, instead leaving the ball in the court of EU leaders to make a move.

The No 10 spokeswoman said: “I think he has been clear that the backstop has to be abolished. He remains confident that the EU will stop claiming that the withdrawal agreement cannot be changed. But until that happens we must assume that there will be a no-deal Brexit on 31 October.”

Responding to Johnson’s refusal to meet EU leaders without a promise to scrap the backstop, one EU source said: “This choice puts us on the path towards no deal, which is the worst possible way to manage the consequences of Brexit.”

Others detected nothing new in Johnson’s bravado. “As Mandy Rice-Davies once said in a court case in the 1960s, ‘he would say that, wouldn’t he’,” an EU diplomat said. “The demand for a new withdrawal agreement is simply not realistic, it is not in this world.”

Some wondered whether the British government should be taken seriously. “I am not sure what he is playing at,” one diplomat said. “It takes you two minutes to realise the backstop is important to the EU, you don’t need to be a big Brexit expert. Either you are not talking, or this is for another audience, and I hope it is the latter.”

EU leaders should seek to meet the new incumbent at No 10, the diplomat suggested, “to filter out what he means and what he is saying to a domestic audience”.

A European commission spokesperson referred to a phone call between Juncker and Johnson last week, when the outgoing commission president outlined that the bloc would not change the Brexit agreement finalised with Theresa May, but remained open to changing the political declaration text.

The spokesperson said: “We have agreed a withdrawal agreement with the United Kingdom government. The deal we have achieved is the best deal possible. We are willing to add language to the political declaration, but we will not reopen the withdrawal agreement.”

Earlier, Raab refused to say whether Johnson was planning to see EU leaders any time soon, saying there would be meetings “in due course”.

Facebook Twitter Pinterest Dominic Raab arrives to attend a cabinet meeting on Monday. Photograph: Chris J Ratcliffe/Getty Images

Johnson is ramping up planning for no deal with a series of new cabinet committees to prepare for leaving on 31 October.

The government is also planning an advertising campaign involving spending up to £100m on warning the public and business to get ready. Johnson’s spokeswoman could not say what the exact messages would be or whether the public would be advised to stockpile. It will not involve leafleting every household, but broadcast and billboard advertisements are likely.

David Frost, Johnson’s new chief Brexit negotiator, has warned his European counterparts not to underestimate the prime minister. According to a leaked email seen by the Financial Times, Frost sent an email telling them that “you should be in no doubt about this government’s commitment to the 31 October date”.

It added: “I would also add that many people are inclined to underestimate Boris Johnson and I would urge you not to do so.”

However, unlike the prime minister, Frost has been seeking to meet MEPs, requesting meetings this week with the European parliament’s pointman on Brexit, Guy Verhofstadt. The Belgian MEP and senior parliament officials were not available to see Frost because they were not in Brussels.

On his visit to Scotland, Johnson heaped praise on the Scottish Conservative leader, Ruth Davidson, who on Sunday issued a defiant challenge to the prime minister, pledging that she will refuse to back a no-deal Brexit.

Claiming that he was “with Ruth in wanting to avoid a no-deal Brexit”, he said: “Ruth has been a fantastic leader of the Scottish Conservatives. I am lost in admiration for what she has achieved. I’m a massive fan of the way she has taken the argument to those who would destroy our union.”

Davidson has made no secret of her reservations about the new prime minister, and Johnson infuriated her last week by sacking her ally David Mundell as Scottish secretary against her advice.

The first minister, Nicola Sturgeon, said she intended to set out for Johnson the “considerable damage” that any Brexit, and especially a no-deal Brexit, would do to Scotland’s economy.

Speaking in advance of her first face-to-face meeting with Johnson since he became prime minister, she said: “Boris Johnson has formed a hardline Tory government with one aim: to take Scotland and the UK out of the EU without a deal.”