EMMANUEL Macron has fired a warning shot at Boris Johnson, insisting the Irish backstop is “indispensable" to stability in Ireland and to the integrity of the single market.

The French President, who welcomed the Prime Minister to the Elysee Palace, said ahead of talks over lunch that the Withdrawal Agreement sealed with Theresa May could not be “reshuffled”.

At a brief joint news conference, he noted that while he had been portrayed as the EU’s "hard man," he was simply being clear about where he stood.

"My position has always been to respect the sovereign choice made by the British people to leave the European Union. I regret it. Had I been a British voter I would have made a different choice but I respect democracy and the wishes of people and I, therefore, believe we now have to implement this choice."

But he emphasised that his position was based on "protecting and strengthening the European project".

Stressing the Withdrawal Agreement did “not belong to any member of the EU alone to negotiate or to renegotiate," the President said: “The key elements of this agreement, including the Irish backstop, are not just technical constraints or legal quibbling, but indeed genuine, indispensable guarantees to preserve stability in Ireland [and] to preserve the integrity of the single market which is the foundation of the European project.”

The French leader backed Angela Merkel's call for the UK to come forward with proposals within 30 days.

"What Angela Merkel said yesterday and which is very much in line with the discussions we have had since the very beginning is that we need visibility in 30 days," explained Mr Macron. "I believe that this also matches the goal of Prime Minister Johnson. No one will wait until October 31 to find the right solution."

But he pointed out it would not be possible to find a new withdrawal agreement "very different from the existing one" within a 30-day timescale.

And yet he held out a potential glimmer of hope to his guest, when he suggested an answer could be reached "without reshuffling" the existing deal.

"We should all together be able to find something smart within 30 days if there is goodwill on both sides," declared Mr Macron.

But he also said what Michel Barnier, the EU’s chief negotiator, had agreed with the May Government “can be amended” if the changes complied with his two goals of maintaining the integrity of the single market and the stability of Ireland.

The PM made clear to his host that this was indeed do-able but noted that while he wanted a new agreement, the UK "must come out of the EU on October 31; deal or no-deal".

He went on: "I want to make it absolutely clear to you Emmanuel - to the French people - that of course I want a deal. I think we can get a deal and a good deal. I was powerfully encouraged by our conversations last night in Berlin with our mutual friends.

"I know that with energy and creativity and application we can find a way forward for all our businesses and our citizens.”

Mr Johnson stressed that it was “vital for trust in politics” that governments acted on the results of referendums.

"Then, of course, we can take our relationship forward. I agree with you wholeheartedly Emannuel that it is a quite extraordinary relationship," said the PM.

Mr Johnson again made clear the UK, “under no circumstances,” would introduce a hard border with the Republic.

"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,” he said, referring to alternative arrangements like trusted trader and electronic pre-clearing of goods.

"A great deal of work has already been done to ensure that the transition on October 31 is as smooth as it possibly can be and so there are already agreements on aviation, on financial services, many other sectors and what we want to do in the next 71 days or whatever is remaining, we want to make sure we do all the necessary work on both sides of the Channel to make sure that whether we get an agreement or not our exit is as smooth and pain-free as possible for citizens and businesses on both sides," explained the PM.

He added: "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 October 31. Let's get on now in deepening and intensifying the friendship and partnership between us.”