The pension system, the most costly in , will collapse in 20 years if a major change is not introduced, experts have warned. Analysis by the France's Council on Retirement Policy said that the structure will become unviable by 2045 if the retirement age is not increased to 66. It comes after France's President, , sparked fury two years ago after raising it to 64. Now, he has been told that he faces a "social explosion" if another increase were enforced.

The report argues that, without a further increases in the retirement age, France would become bankrupt, The Times reports. Experts note that 25% of French public spending is devoted to pensions, and this is rising steadily, despite reform. If the state pension age remains at 64, the pension deficit is predicted to reach €15billion by 2035.

Sophie Binet, head of the militant CGT union, said: "We will not let them destroy our hard-won rights."

Jean-Luc Mélenchon, leader of the radical left-wing France Unbowed party, said: "This is a declaration of war on the French people.

"Macron and his technocrats want to turn retirement into a privilege for the rich. We will bring the country to a standstill if they persist."

In January, French Prime Minister Francois Bayrou announced a renegotiation of the government's plan to raise the retirement age.

"I'm choosing to put this subject back on the agenda, with the social partners, for a short time and under transparent conditions," he said.

He also promised to aim to attain "a new path of reform, without any totems or taboos, not even the retirement age," as long as the financing for the changes is guaranteed, reported.

MP Mathilde Panot, who chairs the parliamentary group of the France Unbowed party, wrote on X afterwards: "Bayrou has just lied and betrayed his commitment on pensions. Exactly as we predicted."

In February, the Prime Minister launched a "conclave", a weekly meeting during which trade union and business group leaders discuss with the government how to improve the pensions system, reports.