Mr Barnier, 70, former EU chief Brexit negotiator, is now in the running to become France’s next president. After announcing his surprise candidacy in August, Barnier edged out his rivals in the race to become the top candidate of the center-right Les Républicains (LR) party. The party will hold primary elections next month to decide who will face President Emmanuel Macron and far-right leader Marine Le Pen in the April vote.
Mr Barnier is known to many in the UK as the head of the EU negotiating team, which led the talks on behalf of Brussels regarding Britain’s exit from the bloc.
After four and a half years of arduous negotiations, Mr Johnson announced on Christmas Eve last year that the two sides had finally agreed to the trade and cooperation agreement.
The British Prime Minister has been heavily criticized by Mr Barnier in his book “My Secret Brexit Diary: A Glorious Illusion”, published in May this year.
The veteran of French politics will not “appease” Mr Johnson if he becomes French president, according to Dr Paul Smith, an expert on French politics.
The scholar is associate professor of French history and politics at the University of Nottingham.
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He told Express.co.uk: “I wouldn’t expect Barnier to be more appeasing to Johnson than Macron or even Le Pen or any of the other candidates.
“If there is a candidate who does not really have an understanding or empathy towards the other powers, it is Le Pen.
“I wouldn’t expect Barnier, rhetorically at least, to be more conciliatory towards the UK than Macron was, and I certainly wouldn’t expect Le Pen. “
Mr Barnier lashed out at the UK negotiating team in his book, calling them ‘childish’ and ‘not up to the task’.
In his 500-page account of the Brexit talks, he described Mr Johnson as “like a bulldozer” during a period of negotiations in 2019.
“But again, we’ve got our nerves under control.”
Speaking of the incident, Mr Barnier quoted an aide as saying, “We always knew we were going to hit a crisis.
“Now that we’re here we need to do what we always said we would do and be the ‘adults in the room’.”
Dr Smith said that while Barnier may have criticized Mr Johnson and the UK before, his success or failure in the French presidential election will be determined by national issues.
He said: “None of the French presidential candidates will win the election on the basis of being agreeable or disagreeable to the British.
“Actually, the French electorate doesn’t care much about Britain – why would they? – no more than the British electorate cares about the French.
“It’s very rare that someone wins an election on the basis of foreign policy.
“The last person who won an election on the basis of foreign policy was probably Margaret Thatcher in 1983 when she used the Falklands factor to hold a snap election.”