The EU’s chief Brexit negotiator Michel Barnier says he is “strongly opposed” to key parts of Theresa May’s proposals for a post-withdrawal trade deal.

In a fresh blow to the British prime minister’s Chequers plan, which triggered senior cabinet resignations and faces growing opposition from hardline Tory Brexiteers, Mr Barnier says a suggested “common rulebook” for goods would kill the European project.

He told German newspaper Frankfurter Allgemeine Zeitung: “We have a coherent market for goods, services, capital and people – our own ecosystem that has grown over decades. You cannot play with it by picking pieces.

“There is another reason why I strongly oppose the British proposal. There are services in every product. In your mobile phone, for example, it is 20 to 40 per cent of the total value.”

Mr Barnier also told EU car manufacturers they would have to use fewer British parts after Brexit to keep to tariff export rules.

The tough comments came as former Brexit secretary David Davis branded the Chequers blueprint as being “actually almost worse than being in” the EU. 

Mr Davis poured scorn on Ms May’s claim that she would not be “pushed into accepting compromises on the Chequers proposals that are not in our national interest” as that risked becoming an “an incredible open sesame to all”.

Theresa May insists she will not be forced into watering down her Brexit plan. Photo: Getty

“The coming months will be critical in shaping the future of our country and I am clear about my mission,” Ms May wrote in the Sunday Telegraph newspaper.

Ms May also said she would not hold a second referendum on Britain’s EU membership, reiterating a long-held position in an attempt to counter increasingly vocal campaigning for another public vote on the terms of the divorce.

“To ask the question all over again would be a gross betrayal of our democracy,” she said.

Mr Davis told BBC One’s The Andrew Marr Show: “In my view, the Chequers proposal … is actually almost worse than being in.

“We will be under the rule of the EU with respect to all of our manufactured goods and agri-foods, that’s a really serious concession; what about take back control, it doesn’t work?

“That actually leaves us in a position where they dictate our future rules without us having a say at all, so it’s a worse deal.”

In another sign of cabinet tensions, International Development Secretary Liam Fox took a swipe at the Treasury over gloomy predictions on the consequences of a no-deal scenario.

Mr Fox told the BBC: “Can you think back in all your time in politics where the Treasury have made predictions that were correct 15 years out, I can’t. They didn’t predict the financial crisis that happened; no one could.

“So this idea that we can predict what our borrowing would be 15 years in advance is just a bit hard to swallow.

“To say what a GDP figure would be 15 years ahead is not a predictive power that I’ve known the Treasury to have in my time in politics … I don’t believe it is possible to have a 15-year time horizon on predictions on GDP.”

The comments followed reports that election strategist Lynton Crosby, who masterminded Boris Johnson’s successful London mayor campaigns, is manoeuvring to derail the PM’s EU withdrawal agenda with a co-ordinated national campaign.

Mr Barnier added: “By the way, the British have a choice. They could stay in the single market, like Norway, which is also not a member of the EU – but they would then have to take over all the associated rules and contributions to European solidarity. It is their choice.

“But if we let the British pick the raisins out of our rules, that would have serious consequences. Then all sorts of other third countries could insist that we offer them the same benefits. That would be the end of the single market and the European project.”

-AAP