George Galloway has been referred to the police by the MPs expenses watchdog following a complaint by his former assistant.
Aisha Ali-Khan accused the former Bradford West MP of using her time as a taxpayer-funded assistant for personal errands, such as clothes shopping and preparations for his wedding, rather than official parliamentary work.
The Independent Parliamentary Standards Authority (Ipsa) has now passed on the claims to Metropolitan Police.
Ali-Khan's lawyers say the claims amounted to a breach of obligations to use parliamentary funds for associated functions and activities only.
Galloway, who recently lost his Bradford West seat at the general election to Labour's Naz Shah, previously denied the allegations.
A spokesperson for Ipsa said: "Ipsa's compliance officer has completed his assessment of the George Galloway complaint and has passed it on to the Metropolitan Police Service."