The Union Jack flag is seen flying at the British Council in Paris, France, December 19, 2018. REUTERS/Charles Platiau

PARIS (Reuters) - It would be wrong for Britain to think the European Union will blink on Brexit and make concessions that undermine its core principles, such as the integrity of the single market, an official at the French presidency said on Wednesday.

“If there’s an idea going round that the European Union has shown a firm front but in fact is weak and febrile when it comes to its fundamental principles, well that would be wrong,” said the official at President Emmanuel Macron’s office.

“Nobody believes it, and I don’t think Theresa May believes it,” the official added, a day after the British prime minister’s deal over the terms for divorce from the bloc was resoundingly defeated by the British parliament.

The French official added that any request by Britain to extend article 50 would have to come with a plan, a strategy, that would respect EU principles to be approved by the EU side.

“An extension is not a solution in itself, a procedure exists and it must be the consequence of a plan. The work must be done in London in coming days, because it is not Brussels which is blocking things,” he said.

“All the options would be looked at with good will and openness, as long as they respect the main principles of the EU, notably the integrity of the single market,” the official added.

The French official also said the wide margin by which the vote in the Commons was lost demonstrated that further political assurances from the EU alone would not be enough to swing a new vote.

France’s prime minister will hold a meeting with cabinet ministers on Thursday morning to provide an update on ongoing preparations for a no-deal scenario and speed them up if need be, the official added.