France's opposition Socialists face a run-off vote for a new leader, after a first ballot did not produce a winner.
A vote to choose the leader of the French Socialist opposition has been won by Martine Aubry, the party says.
The second vote on Friday, which comes amid bitter party rifts, pits former presidential candidate Segolene Royal against Lille Mayor Martine Aubry.
A former minister and current mayor of Lille, Ms Aubry is best known as the architect of 35-hour work week.
Leftist MEP Benoit Hamon is out of the race after coming third in Thursday's vote. None of the candidates gained the 50% needed to avoid a run-off vote.
Official results say she defeated ex-presidential candidate Segolene Royal by 42 votes, a razor-thin margin. Ms Royal is contesting the result.
The leadership issue is being decided by 233,000 party members.
The party has been divided over whether to move toward the political centre or hold to traditional leftist beliefs.
The voting comes after last weekend's party congress - that was meant to back a single candidate - ended in disarray.
Ms Aubry, 58, won 50.02% in a second ballot of party members. Ms Royal scored 49.98%.
In the first round, Ms Royal gained 42.5% of the vote, Ms Aubry 34.7% and Mr Hamon 22.8%.
"I am not going to take this," Ms Royal told AFP news agency.
After the count, Mr Hamon - who is seen by some as being too far-left - urged those who had backed him to vote for Ms Aubry in the second round.
But Ms Aubry rejected her proposal to hold a new vote. She will be the first female to head the French Socialists.
"For our party to remain firmly anchored to the left, I ask those who supported me to vote massively for Aubry," he said.
Party infighting
The party has been beset by infighting since France's last Socialist President Francois Mitterrand stepped down in 1995.
The election went to a second round after a first ballot on Thursday failed to produce a winner with more than 50% of votes.
Tough job
Ms Royal gained 42.5% of the vote, Ms Aubry 34.7% and Leftist MEP Benoit Hamon 22.8%.
The candidates are vying to replace outgoing chief Francois Hollande.
Mr Hamon dropped out and urged those who had backed him to vote for Ms Aubry in the second round.
Ms Aubry has said she wants to reform the party while also upholding its "leftist values".
Ms Royal - who had won a pre-convention ballot with 29% of members' votes - accused her rivals of clinging to "outdated" ways after they refused to rally behind her leadership bid.
One of the candidates, Paris Mayor Bertrand Delanoe, even pulled out of the race to "avoid creating further confusion".
Ms Royal, defeated by centre-right President Nicolas Sarkozy in last year's election, had said she wanted to renew the party and put it in a position to beat the conservative candidate in 2012.
"The Socialist Party is gravely ill," Mr Delanoe said. He has urged party members to back Ms Aubry, as has Mr Hollande.
There has not been a Socialist president since Francois Mitterrand won a second term in 1988.
'Ungovernable'
Ms Royal has been accused of seeking to transform the party into her own personal electoral machine, says the BBC's Emma Jane Kirby in Paris.
Ms Royal, defeated by Mr Sarkozy in last year's presidential elections, has been accused of seeking to transform the party into her own personal electoral machine, the BBC's Emma Jane Kirby in Paris says.
Supporters had hoped she could reform the party and bring it towards the centre, but critics, especially among the party's old guard, have accused her of being politically inconsistent.
Supporters hope she can reform the party and bring it towards the centre, but critics, especially among the party's old guard, accuse her of being politically inconsistent.
The voting took place after last weekend's annual party congress - that was meant to back a single candidate - ended in disarray, with top party members failing to reach consensus on a new leader.
Ms Royal accused the grandees of "teaming up to block the renewal of the party" and urged them to "let the grassroots members decide".
Ms Aubry, the architect of France's 35-hour week and daughter of former European Commission President Jacques Delors, is seen by some younger members as being too old-fashioned, our correspondent says.
After Thursday's vote she said she was committed to "deep changes" in the party, but still wanted to ensure it "defends leftist values."
France's media have said the Socialists showed themselves at the Reims convention to be "ungovernable".
France's media have said the Socialists showed themselves at the Reims convention to be "ungovernable".
It is clear that whoever becomes the new leader of the opposition will have a tough job uniting party members to build a credible challenge to President Sarkozy's government, our correspondent says.
