THERESA May’s bid to persuade France of the benefits of her Chequers plan for a soft Brexit has been derailed in advance by the EU’s top negotiator trashing key parts of it.

Michel Barnier’s intervention undermined the Prime Minister on the eve of today’s meeting with President Macron at Fort de Brégançon, his state residence on the Côte d’Azur.

In an article published in 20 newspapers across Europe, Mr Barnier said some of the UK’s proposals would undermine the single market and threaten the EU.

Mrs May is cutting short a holiday in Italy to visit the French president as part of wider cabinet effort to woo individual nations on the merits of the Chequers plan.

Foreign Secretary Jeremy Hunt was in Austria earlier this week, warning a failure to agree a Brexit deal based on the plan would be a “huge geo-strategic mistake”.

Brexit Secretary Dominic Raab was also in France yesterday promoting the scheme.

The UK proposal would see a “common rule book” between the UK and the EU on goods and and agri-food, but greater freedom on services and migration.

Mr Barnier’s article reinforced the EU view that this was unacceptable “cherry picking”.

Although his argument was familiar, his timing was seen as a pointed snub to the PM.

It also jarred with reports that German Chancellor Angela Merkel was ready to back a so-called “blind Brexit”, a vague fudge which would help Mrs May avoid a no-deal Brexit.

However, in better news for Mrs May, Mr Barnier also said the EU would be more flexible on the key issue of a backstop for trade and customs in Northern Ireland.

He wrote: “Let's be frank: as the UK has decided to leave the Single Market, it can no longer be as close economically to the rest of the EU.

“The UK wants to leave our common regulatory area, where people, goods, services and capital move freely across national borders.

“These are the economic foundations on which the EU was built. And the European Council - the 27 Heads of State or government - as well as the European Parliament have often recalled that these economic foundations cannot be weakened.”

He went on: “The UK knows well the benefits of the Single Market. It has contributed to shaping our rules over the last 45 years.

“And yet, some UK proposals would undermine our Single Market which is one of the EU's biggest achievements.

“The UK wants to keep free movement of goods between us, but not of people and services. And it proposes to apply EU customs rules without being part of the EU's legal order.

“Thus, the UK wants to take back sovereignty and control of its own laws, which we respect, but it cannot ask the EU to lose control of its borders and laws.”

He said the biggest risk caused by Brexit was in Ireland, with the need to avoid a hard border between north and south.

“What the EU has proposed is that Northern Ireland remains in a common regulatory area for goods and customs with the rest of the EU. We are ready to improve the text of our proposal with the UK,” he said.

It was reported that Environment Secretary Michael Gove privately discussed the UK being “parked” in the European Economic Area alongside Norway after Brexit to avoid a no-deal.

The Financial Times reported the Brexiter floated the option at a dinner of moderate Tory MPs and peers on June 25, before the Chequers plan was decided.

German reports said Mrs Merkel was considering a blind Brexit involving hazy declarations on intent rather than a formal treaty to help the Prime Minister.

Labour MP Chris Leslie of the People’s Vote campaign, which wants a referendum on the Brexit deal, said the EU should not offer Mrs May a face-saving way-out.

He said: “A blind Brexit would take the UK to the same place as a no-deal Brexit, but without the clarity. The idea that the fundamental contradictions of the government’s Brexit policy can be more easily resolved after the UK has left the EU is simply ludicrous.

“A blind Brexit is being talked about because some see it as a short-term face-saving deal for both the British government and the European Union, both of which are now terrified that concluding with a failure to agree a deal will result in a humiliating no-deal Brexit.

“With the EU27 governments and the EU commission wanting to spare Theresa May’s blushes, there is a risk we end up with a fake deal to save face.”