Reims, France - France's opposition Socialist Party failed to decide on a candidate for the post of party leader Sunday after lengthy negotiations that lasted through the night.

It is the first time in decades that the party conference has not been able to come up with a compromise candidate to present to party members.

After the night of deliberations in Reims, about 150 kilometres to the north-east of Paris, the race seemed to be between Segolene Royal, the party's presidential candidate who was beaten by Nicolas Sarkozy last year, and Martine Aubry, a former labour minister.

"Now it is up to you to decide this party's leadership," said Royal in an address to party members, who will vote on the party's leadership on Thursday.

Earlier, she had said she was disappointed that her "outstretched hand" had not been accepted.

The party conference had been expected to decide on a compromise for the leading candidates. But in polling, which reflected support for the candidates' platforms and not the candidates themselves, Royal only received 29 per cent of the vote.

Aubry and Paris Mayor Bertrand Delanoe each received 25 per cent. Delanoe removed himself from the running without endorsing either candidate.

Surprisingly, Benoit Hamon, from the party's far-left wing, garnered 19 per cent of the vote.

If none of the candidates receive a clear majority on Thursday, the party would have to hold a run-off election on Friday.

A major sticking point was whether the Socialists would be prepared to work in coalition with the centrist Modem party.

Royal's opponents, Aubry and Delanoe, have ruled out such a move. Royal has said she thinks cooperation with Modem makes sense, but said she would put the question to a party vote.

Socialist Party leader and Royal's former partner, Francois Hollande, is stepping down after 11 years in office.