Emmanuel Macron has described the Irish backstop as “indispensable” to a Brexit deal and urged Boris Johnson to set out his proposed alternatives as soon as possible, as he met the British prime minister in Paris.

The French president told Johnson on Thursday that the EU would like “visibility” on London’s concrete proposals for the UK’s withdrawal from the EU within a month, echoing language used by the German chancellor, Angela Merkel, on Wednesday.

Emmanuel Macron tells Boris Johnson backstop is 'indispensable' – live Read more

Macron said he stood united with Merkel that the clock was ticking and that it was not possible to wait until the last minute to find a solution. He said the EU’s chief negotiator, Michel Barnier, could be involved in finding an answer “without totally reshuffling the withdrawal agreement”.

“We should all together be able to find something smart within 30 days if there is goodwill on both sides,” Macron said. “We need to try to have a useful month.”

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

Merkel insisted on Thursday that she had not given the UK a strict 30-day deadline, but instead wanted to highlight how short time was before the UK’s planned exit date of 31 October.

Any new proposals to deal with the issue of the Northern Ireland border should fit into the existing framework withdrawal agreement already negotiated, Macron said.

Johnson has repeatedly said the backstop – an insurance plan to avoid a hard border on the island of Ireland – must go in order to avoid a no-deal exit. He argues it could leave the UK tied to the EU indefinitely.

But Macron said the backstop was both an indispensable guarantee for the stability of Ireland and a means of protecting the integrity of the European single market, and that any new UK ideas had to respect that.

Johnson arrived at the Élysée Palace in a Range Rover decorated with UK flags. Macron is keenly aware of the prime minister’s long track record of French-bashing for a domestic audience, but both men were at pains to show their close working relationship. Johnson repeatedly called Macron “Emmanuel” and smiled at him, only shrugging and grimacing slightly and reaching into his jacket for a pen to amend his speech as he stood listening to Macron say the Irish backstop was an “essential guarantee”.

An official in Macron’s office said the talks were constructive.

Facebook Twitter Pinterest Macron and Johnson in the Élysée on Thursday. Photograph: Christophe Petit-Tesson/AFP/Getty Images

At a joint news conference on Wednesday in Berlin with Johnson, Merkel appeared to suggest that a solution to the sticking point of the Irish backstop could be found in the next 30 days. But on Thursday she said: “It is not about 30 days. The 30 days were meant as an example to highlight the fact that we need to achieve it in a short time.”

Macron was careful to say that if no concrete solution based on the current withdrawal agreement were found in the coming month, it would be the UK’s sole responsibility. “It would mean that the problem is deeper, more political – a British political problem.” At that point “there will be a political choice to be made by the prime minister, it won’t fall to us”.

Macron appeared to have the upper hand as he smiled warmly while telling Johnson: “On Brexit my position is clear and I know how much that occupies your days and your nights.”

This appeared to be a reference to Downing Street rushing to respond on Wednesday night to Macron’s comments to reporters in Paris that Johnson’s written request to renegotiate the UK’s exit and scrap the backstop was “not an option”.

Macron was even more tactile than usual with a foreign leader, repeatedly patting Johnson on the back and shoulder.

“I’ve always been portrayed as the toughest in the group,” Macron grinned. Political commentators in France suspect Johnson of wanting to frame France as the bad cop to blame for any no deal. Macron is determined to avoid taking any blame for what he calls the UK’s internal political crisis over Brexit.

Macron said he believed the British people’s sovereign decision must be carried out, warning against “democracies suffering lack of efficiency and lack of clarity”.

Facebook Twitter Pinterest Macron was more tactile than usual with a foreign leader. Photograph: Chesnot/Getty Images

He reminded Johnson that he stood firmly together with Merkel in a united position and that it was not up to any one single EU member state to negotiate.

Johnson tried to strike a positive note, saying that he admired the “can-do spirit” expressed by Merkel in Berlin on Wednesday.

He said: “Let’s get Brexit done, let’s get it done sensibly and pragmatically and in the interests of both sides and let’s not wait until 31 October. Let’s get on now in deepening and intensifying the friendship and partnership between us.

“When you look at the border with Northern Ireland ... under no circumstances will the UK government be instituting, imposing checks or controls of any kind at that border. We think there are ways of protecting the integrity of the single market and allowing the UK to exit from the EU, all and entire and perfect as it were.”

Q&A What does a no-deal or WTO-rules Brexit mean? Show Hide If the UK leaves the EU without a deal it would by default, become a “third country”, with no overarching post-Brexit plan in place and no transition period. The UK would no longer be paying into the EU budget, nor would it hand over the £39bn divorce payment. The UK would drop out of countless arrangements, pacts and treaties, covering everything from tariffs to the movement of people, foodstuffs, other goods and data, to numerous specific deals on things such as aviation, and policing and security. Without an overall withdrawal agreement each element would need to be agreed. In the immediate aftermath, without a deal the UK would trade with the EU on the default terms of the World Trade Organization (WTO), including tariffs on agricultural goods. The UK government has already indicated that it will set low or no tariffs on goods coming into the country. This would lower the price of imports – making it harder for British manufacturers to compete with foreign goods. If the UK sets the tariffs to zero on goods coming in from the EU, under WTO “most favoured nation” rules it must also offer the same zero tariffs to other countries.

WTO rules only cover goods – they do not apply to financial services, a significant part of the UK’s economy. Trading under WTO rules will also require border checks, which could cause delays at ports, and a severe challenge to the peace process in Ireland without alternative arrangements in place to avoid a hard border.

Some no-deal supporters have claimed that the UK can use article XXIV of the General Agreement on Tariffs and Trade (Gatt) to force the EU to accept a period of up to 10 years where there are no tariffs while a free trade agreement is negotiated. However, the UK cannot invoke article XXIV unilaterally – the EU would have to agree to it. In previous cases where the article has been used, the two sides had a deal in place, and it has never been used to replicate something of the scale and complexity of the EU and the UK’s trading relationship. The director general of the WTO, Roberto Azevêdo, has told Prospect magazine that “in simple factual terms in this scenario, you could expect to see the application of tariffs between the UK and EU where currently there are none”. Until some agreements are in place, a no-deal scenario will place extra overheads on UK businesses – eg the current government advice is that all drivers, including lorries and commercial vehicles, will require extra documentation to be able to drive in Europeif there is no deal. Those arguing for a “managed” no deal envisage that a range of smaller, sector-by-sector, bilateral agreements could be quickly put into place as mutual self-interest between the UK and EU to avoid introducing or to rapidly remove this kind of bureaucracy. Martin Belam

Johnson added that “technical solutions” were “readily available” to avoid checkpoints, but did not spell out his clear alternative to a backstop guarantee.

The prime minister is due to meet the European council president, Donald Tusk, at the G7 summit this weekend, their first encounter since Johnson took over, an event that was greeted by a frosty two-line letter of congratulations from the EU leader.

Tusk, who will be representing the EU at the G7, previously said there was “a special place in hell” for those who promoted Brexit “without even a sketch of a plan” – remarks seen as being aimed at Johnson, a figurehead of the leave campaign.

Tusk will be “in listening mode in Biarritz” and the EU is “looking forward to new facts and new workable ideas”, a senior EU official said. But hopes of a breakthrough are low, with both sides emphasising that the bilateral meeting will also address the global economy and foreign policy questions.

No deal has become the default scenario for EU officials, since Johnson wrote to Tusk on Monday calling on the EU to scrap the backstop, the insurance plan to avoid a hard border on the island of Ireland.

Since that letter and Johnson’s statements that he believes a no deal could take place, “the EU and our member states need to take that possibility of a no-deal outcome much more seriously than before”, a senior EU official said. “I know that this [no deal] is the working assumption. Because we are responsible people, we have to prepare ourselves for that, the worst possible outcome – but still likely – if you listen to the declarations of Prime Minister Johnson.”