Mr Barnier – who is running for the French presidency against Emmanuel Macron – said it was time for France to “regain sovereignty” lost to the European judiciary.
The politician who negotiated the Brexit deal on behalf of Brussels appears to have adopted Eurosceptic rhetoric in his bid to win the presidency for the centre-right Republicans.
“We must regain our legal sovereignty in order to no longer be subjected to the judgements of the European Court of Justice or the European Court of Human Rights,” the former EU Commissioner said on Thursday.
Mr Barnier repeated his call for a referendum to impose a five-year moratorium on immigration to France from outside the EU. “We will propose a referendum in September 2022 on the question of immigration,” he told a rally in Nimes.
Mr Barnier later issued a tweet attempting to clarify his rally remarks – saying he did not want France to break entirely free of the European courts but to create a “constitutional shield” to give the country more power over immigration issues.
“Let us keep calm,” the presidential candidate also tweeted, claiming he wanted to “avoid any unnecessary controversy”.
While some found Mr Barnier’s remarks “ironic” – given his stance defence of freedom of movement during the Brexit process – others said he was in danger of “destroying his legacy”.
“One wonders how a sentence like that can come from such a committed European,” Clément Beaune, France’s junior minister for EU affairs, told Politico on his latest remarks.
Julien Hoez from the European Liberal Forum said: “Michel Barnier is giving a masterclass on how to destroy your career and legacy in the desperate hope of looking electable to an electorate that just straight up dislikes you regardless.”
The Republican candidate, who left the EU Commission in March after hitting its mandatory retirement age of 70, was one of the most prominent face of Brexit negotiations – continually criticising Brexiteers in the Conservative party.
Responding to his attack on the European courts, Tory MP Simon Clarke tweeted: “This is ironic in the extreme.”
Polls in France have next year’s contest as a race between incumbent Mr Macron and far-right National Rally candidate Marine Le Pen.
But Mr Barnier is hoping to make a strong showing in the first round of the contest, which is scheduled for April 2022.