The Napthine government's hope that its most troublesome planning controversy was behind it has been dashed by Ombudsman George Brouwer's decision to launch an investigation into the botched rezoning of farmland at Ventnor on Phillip Island.

Responding to a written complaint from the Labor opposition, Mr Brouwer has confirmed an inquiry that threatens to further embroil senior Liberal figures - including Planning Minister Matthew Guy, former premier Ted Baillieu and Abbott government minister Greg Hunt - in one of the murkiest planning sagas in recent Victorian history.

Carley Nicholls and James Hopkins purchased the Ventnor property on Phillip Island. Credit:Simon Schluter

The Liberals had sought to bury the long-running Ventnor ruckus in August with a multimillion-dollar out-of-court settlement.

The deal silenced the aggrieved parties to the proposed sale of the 24 hectares of land in 2011 - owner/vendor John Cadogan and purchasers Carley Nicholls and husband Jim Hopkins.