* New book digs up alleged graft among Socialists
* Election favourite Hollande accused of not blowing whistle
* Timing awkward nine weeks from presidential election
By Thierry Lévêque
PARIS, Feb 24 (Reuters) - A slew of corruption scandals on French Socialist turf have become an unwelcome distraction for the presidential campaign of Francois Hollande, as opponents accuse the frontrunner of ignoring shady behaviour during a decade as party leader.
The cases have cropped up in Socialist fiefdoms from the northern Pas-de-Calais region and city of Lille - where former IMF chief Dominique Strauss-Kahn was questioned this week in a prostitution case - to the southern port city of Marseille.
As France gears up for its April-May election, the cases have provided further ammunition for the conservative UMP party and far-right National Front to attack Hollande, who polls show could win a May 6 run-off round.
Hollande, who led the Socialists as first secretary for 11 years, has not been accused of wrongdoing.
Accusations of misusing public funds and influence-peddling for construction deals concern local-level officials. But opponents say Hollande knew about shady practices and did nothing to stop them.
"Mr. Hollande ... must have known," Sebastien Huyghe, a senior UMP official, said this week. "He talks of an irreproachable republic, when he was the first to cover up this sort of depravity."
In a book called "The Rose Mafia", published on Thursday, a Socialist former mayor in northern France describes a well-oiled system of kickbacks and favour-trading between local businessmen and a high-ranking Socialist official.
"How can you believe that neither (Socialist Party First Secretary Martine) Aubry nor Hollande were ever informed of shady dealings and excesses in the Pas-de-Calais federation?" the author, Gerard Dalongeville, asks in the book.
Hollande has not responded to the accusations.
Aubry, mayor of Lille and Hollande' successor as Socalist Party head, has brushed off the allegations as the work of a man with a dubious record. Dalongeville spent eight months in police custody in 2009 and is under investigation in a probe into embezzlement in Pas-de-Calais.
"As far as I'm concerned Mr. Dalongeville is not credible, I don't hear him, I don't listen to him," Aubry told LCP television on Wednesday.
Others, however, have said there is no smoke without fire.
Arnaud Montebourg, a prominent lawmaker, has ruffled feathers among fellow Socialists by publicly blowing the whistle on suspected corruption by party officials, both in the Pas-de-Calais region and in Marseille, at a sensitive time.
DSK HANGOVER
Similar accusations have been levied against Hollande - not least from Aubry herself - over corruption in Marseille, a rough-and-tumble port where former local Socialist boss Jean-Noel Guerini is accused of misusing public funds.
In mid-2011, a regional official accused Guerini of running "a mediaeval system of pressure based on fear and intimidation", leading to his taking leave from the Socialist Party, whose presidential primary contest was a few months away.
The case has fuelled attacks by the right-wing Le Figaro newspaper against the Socialist Party, accused of failing to take internal action against Guerini, who retains his seat in Parliament despite being formally under investigation.
Equally rich ground for Le Figaro are the ongoing legal troubles of Dominique Strauss-Kahn, once favoured to become France's next president until he was arrested on a charge, later dropped, of attempted rape in New York last May.
The ex-finance minister was questioned this week as part of an investigation into a prostitution ring that provided girls to the clients of a luxury hotel which Strauss-Kahn frequented.
Accused of knowing that girls brought to him were, in fact, prostitutes paid by local businessmen, Strauss-Kahn was released on Wednesday but remains under informal investigation.
Strauss-Kahn no longer plays a role in politics, but the probe in Lille is fuelling more awkward headlines for the Socialists. Hollande's election campaign manager, Pierre Moscovici, is a close ally of Strauss-Kahn's who defended his name when he was in court in New York last year.
"There may well be, once Dominique Strauss-Kahn's interview is over, interesting news on the practices of Socialist federations in the North and Pas-de-Calais regions," said Nathalie Kosciusko-Morizet, spokeswoman for Sarkozy's campaign.
"If Francois Hollande is where he is today, it's because Dominique Strauss-Kahn is where he is today." (Reporting By Thierry Leveque, writing by Nick Vinocur; Editing by Sophie Hares)
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