Mr Barnier was the EU’s chief Brexit negotiator and played a key role in negotiations with the UK after the 2016 ‘Leave’ vote. The diary will be published under the title “Brexit: The Grand Illusion” with the subheading “Brexit Secret Diary”.

During his time in officer Mr Barnier was involved in high stakes talks with Boris Johnson and Theresa May over Britain’s future EU relationship.

Last December he agreed a new trade deal with Mr Johnson which set the rules for UK-EU trade.

There is speculation Mr Barnier is hoping to run for the French presidency in 2022 in opposition to Emmanuel Macron.

However Express.co.uk readers argued his decision to publish details of private conversations shows why the EU can’t be trusted.

Michel Barnier has warned France could follow the UK out of the EU

One commented: “Once more the EU demonstrate that they cannot be trusted.”

A second added: “My young children do not behave in a tittle tattle manner – the EU looking childish.”

A third posted: “The EU once again showing it is getting more desperate by the day. And that is a good thing.”

Mr Barnier has been promoting his book, which will be available in French and English, via Twitter.

He posted: “For English speakers, happy to announce that my diary will be published in English at the beginning of October.”

A number of Express.co.uk readers argued Mr Barnier’s move represents a personal betrayal of the Prime Minister.

One wrote: “Oh another threat!

“There is nothing you can say Barnier that will discredit Boris more than the EU discredits itself.”

Boris Johnson campaigned fervently for Brexit

Britain formally left the EU in January 2020

A second added: “There you do Boris!!! Don’t bail out their Eurostar!!!

“They will only stab you in the back!!!!”

Another posted: “All Barnier does is make Boris and the UK stronger.”

The Daily Express campaigned strongly for Brexit

Whilst Britain voted to leave the EU in June 2016 this was delayed a number of times and didn’t finally happen until January 2020.

However, until the end of December 2020, when Mr Johnson’s new trade deal came into effect, the UK continued to be a member of the European single market and paid into the Brussels budget.

During this time Britain carried on implementing many European Union made laws.

Britain's EU exit was delayed several times

When the new trade deal came into effect the UK regained its status as a fully independent trading nation.

Recent polling indicates support for Brexit has increased with as many as one in five former Remainers now supporting ‘Leave’.

This has been linked to the EU’s slugging coronavirus vaccine rollout, which is lagging far behind the UK as another virus wave envelops the continent.