Five months before a presidential election that it has every chance of winning, France's main opposition party has reverted to its favourite pastime: shooting itself in the foot.
With its candidate, François Hollande, dominating the opinion polls, the Parti Socialiste has plunged into a vicious civil war over the alleged corruption of senior party officials in northern France.
One of the party's leading figures, Arnaud Montebourg, alleges that police investigations of a local politician in the Pas de Calais point to a long-standing "system of corruption" in the traditional Socialist party heartland. In a leaked letter, Mr Montebourg pointed a finger, without proof, at one of the party's best-known figures, Jack Lang, the former education minister, who represents part of the Pas de Calais in the National Assembly.
Mr Lang, 72, who has started a legal action for defamation, threatened at the weekend to "slap [Mr Montebourg] on both cheeks". The party leader, Martine Aubry, whose own fiefdom in Lille is next to the Pas de Calais, attacked Mr Montebourg without naming him at a party conference on Saturday. She blamed the row on "egotistical publicity-seekers... always in a hurry to spread rumours about their comrades".
The dispute could be profoundly damaging to the Socialist party and Mr Hollande. Police are already investigating another alleged corruption saga in northern France, involving local Socialist party figures, embezzlement and prostitution. The former Socialist finance minister, Dominique Strauss-Kahn, has been linked to this investigation as an alleged frequent guest at sex parties for businessmen, politicians and police chiefs in the Lille area.
The Socialist party is also struggling to contain claims of financial wrongdoing in another electoral heartland, the Marseilles area.
The new affair centres on the mayor of Lièvin, a small former mining community near Lens. Jean-Pierre Kucheida, 67, the Socialist mayor for 30 years, is under police investigation for allegedly taking kickbacks on contracts awarded by agencies created to run social housing and welfare programmes for ex-miners.
Mr Kucheida, who is close to Mr Hollande, denies the allegations but admits making "blunders" in using official credit cards for private expenditure. Ms Aubry last week suspended Mr Kucheida's nomination as a candidate in the parliamentary elections next June, which will follow the presidential election in April and May.
Mr Montebourg, who came third in the Socialist presidential primary in October, inflated a local investigation into a national scandal in a letter to Ms Aubry which was leaked to the press last week. He accused the party leader of being to slow to react to the Marseilles allegations and warned of serious electoral consequences if she did not act to uncover the "system of corruption" in her own backyard.
He added that "the presence of Jack Lang [as a deputy] in the department is only one of the sad symptoms of systematic corruption in the Pas de Calais". Mr Lang, who was parachuted into the area by the party 10 years ago, angrily denies any knowledge of corrupt activities. He is standing down as a northern deputy for "personal and political reasons" and is expected to run in a Paris constituency in June.