(Recasts third paragraph, adds popularity polls)
PARIS, Oct 20 (Reuters) - The partner of the Socialist presidential candidate in France has filed a lawsuit over unverified media claims that police ran secret checks on her, her lawyer said on Thursday.
Valerie Trierweiler is the partner of Francois Hollande who won his party's nomination on Sunday for the election next April.
She filed a lawsuit, lawyer Frederique Giffard said in a statement, against "persons unknown", implying all those involved may not yet have been identified.
Earlier this month, Hollande asked France's conservative government to explain a report published in L'Express weekly that police had run secret checks on his partner.
Trierweiler works for a private TV channel and has been with Hollande since he split from fellow Socialist politician Segolene Royale in 2007.
National police headquarters in Paris denied the report, which had cited police sources as saying the spying focused on Trierweiler's life and relationships. Interior Minister Claude Gueant sued L'Express for defamation.
French President Nicolas Sarkozy and his centre-right camp have accused the Left of seeking to exploit recent developments in a number of anti-graft probes where allies of the president have been investigated.
Sarkozy faces a strong challenger in Hollande - popularity polls have consistently indicated he could beat the incumbent in April with ease. (Reporting By Alexandria Sage; Editing by Robert Woodward)
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