Bertrand Delanoë, the Mayor of Paris, today made a bid for leadership of the Socialist opposition, just as the rudderless French Left risks being upstaged by a new party founded by a revolutionary postman.

Mr Delanoë, 58, France's most popular leftist and most senior gay politician, was the second big beast to enter the fight to succeed François Hollande, the lacklustre outgoing leader. Half a dozen contenders are already in the running for the November party vote, including Ségolène Royal, Mr Hollande's former domestic partner, who lost the run-off for the presidency to Nicolas Sarkozy last year.

The Mayor staked his claim amid media bedazzlement with Olivier Besancenot, 34, a charismatic Trotskyite and second most popular leftist, whose star has soared since he scored four per cent in the presidential first round. A no-compromise Marxist of a type extinct elsewhere, Mr Besancenot is surfing on discontent with both Mr Sarkozy and the parliamentary Left.

Riven with disputes, the Socialists have failed to capitalise on Mr Sarkozy's deep unpopularity. On Sunday Mr Besancenot said that he would do the job and outlined plans for a Nouveau Parti Anti-capitaliste (NPA).

To the delight of Mr Sarkozy's camp, this will drain a substantial fringe of leftists who have given up on the Communist Party and believe that the Socialists have sold out. "French capitalism is in the process of cracking," the baby-faced Mr Besancenot declared to a cheering crowd. "What they need is a good old revolution."

Mr Besancenot's movement, which is opposed to profits, parliamentary democracy and private enterprise, is being credited with a potential 7 or 8 per cent of the national vote. Along with support for a new broad Green coalition, this would fragment the Left just as the far-right Front National of Jean-Marie Le Pen did to the Centre Right of Jacques Chirac in the 1980s and 1990s.

Ms Royal, 54, is the other big contender for the leadership of the self-destructing Socialist party. While the Socialists score well in local government, they have suffered nationally from a lack of leadership since the late President Mitterrand and from a long feud between Marxists and the pro-market Left. "The Socialist party is riddled with depression, dispersion and confusion," the left-leaning Le Monde newspaper said today.

Mr Delanoë scandalised sections of the party last spring when he announced that he was both Socialist and pro-market. Le Monde and Libération, both leftwing newspapers, said today that the Socialists had missed the boat. Just as the party was formally abandoning Marxism and accepting the market, the French were turning against capitalism again because of recession and global upheaval, they said.

Ms Royal and Mr Delanoë are the two most popular Socialists, rating far beyond the half dozen second-rank figures who are jockeying for the leadership. But the broader presidential prospects of both are clouded by liabilities.

In Ms Royal's case it is her image as a mystical-minded lightweight. Mr Delanoë is dogged by his open homosexuality. This matter is taboo in the main media, but it is a source of polemics in the pub and on the internet. Vingt Minutes, an internet news site, today halted comments on its Delanoë report after being swamped with homophobic attacks on the Mayor.

Meanwhile the once powerful Communist party today revealed the extent of its destitution. It reported that it had been forced to let out commercially most of its monumental headquarters on the Place Colonel Fabien, in the old working-class 20th arrondissement. Last month Le Pen sold the Front National's cavernous headquarters at Saint Cloud, on the western Paris outskirts, to pay off debts.

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