Jospin says he does not want to split the party

He had not attracted enough support, and did not want to split the party, he told French radio.

He also said he would not back current Socialist frontrunner Segolene Royal, but did not say who he would support.

He ran for the 2002 presidency, but was beaten into third place by far-right leader Jean-Marie Le Pen.

This prompted a shocked electorate to flock to President Jacques Chirac in the run-off.

Mr Jospin made a tearful comeback this summer at the party conference after four years of political retirement following the presidential rout.

He indicated he could compete for the party's presidential candidacy against Ms Royal and the row of male contenders.

Mr Jospin has signalled he does not agree with Ms Royal's questioning of the 35-hour work week and her tough proposals on law and order.

The party's almost 200,000 members are to elect their candidate for the presidential poll in November.