The Liberal politician resigned today following the release of an Office of Police Integrity report investigating the role of an advisor to Deputy Premier Peter Ryan.

The report, entitled Crossing the Line, looked at the actions of advisor Tristan Weston in relation to a campaign to oust former Victoria Police chief commissioner Simon Overland.

The report says Mr Weston, may face criminal charges following an overwhelming abuse of authority.

Mr Tilley was cited in the report as being a friend of Mr Weston and having organised meetings where they "vented" frustrations about Mr Overland.

They also organised meetings with former deputy commissioner Sir Ken Jones and encouraged the senior office to withdraw his resignation.