French police have raided the lower house of parliament in an investigation into whether the wife of the presidential candidate François Fillon was paid for an allegedly non-existent job, The Guardian reported.

The unusual step, requiring authorisation of the speaker of the lower house, was carried out as part of an inquiry into the “Penelopegate” scandal. It was not immediately clear whether Fillon’s own office was being searched.

Investigators are looking into possible misuse of public funds after a newspaper alleged that Welsh-born Penelope Fillon was paid €500,000 (£430,000) over eight years as his parliamentary assistant for work she did not perform. It is not illegal for French politicians to employ spouses or members of their family, but there is an obligation for them to carry out the job.

Fillon and his wife were questioned separately for five hours on Monday by officers from the anti-corruption brigade. France Inter radio suggested police on were looking for Mrs Fillon’s employment contracts.

Fillon, the centre-right Les Républicains candidate for the April/May presidential election, says he is the victim of a dirty tricks campaign. In a French television interview, he insisted his wife’s work had been “real and legal”.