A restaurant owner in Frankston who stood alongside Matthew Guy and Liberal candidate Michael Lamb to discuss her struggles with rising energy costs on Monday is a convicted cannabis cultivator whom police sought to deny a liquor licence.

Parliamentary hopeful Mr Lamb is also senior sergeant at Frankston police station and by his own account is in charge of every drug investigation in the area.

Matthew Guy and his wife Renae chat with cafe owner Mariam Jamil in Frankston on Monday. Credit:AAP

The Coalition, which has campaigned relentlessly on being tougher on crime than Labor, stumbled on the campaign trail on Monday when it emerged shortly after Mr Guy's campaign bus stopped at the Frankston venue that the owner has a criminal record.

Beach 162 owner Mariam Jamil was convicted of illicit drug cultivation in January 2015.