SECRET police files on people protesting against Victoria's $3.5 billion desalination project are being made available to the private consortium building the plant.

Under a deal struck by the State Government in a bid to ensure the project is finished before Melbourne runs out of water, Victoria Police has agreed to hand over photos, video recordings and other police records to the international consortium AquaSure to help it ''manage'' protests and potential security threats.

Anti-desalination protesters, civil liberties advocates and the State Opposition last night condemned the move as an unacceptable invasion of privacy and a dangerous assault on the democratic right to protest.

The Government signed a memorandum of understanding with Victoria Police and AquaSure on August 28, designed to protect the site at Wonthaggi as well as the electricity supply to the project and new pipelines from the plant to Cardinia Reservoir.

The 20-page document states that Victoria Police ''will release law enforcement data'' to AquaSure, which is made up of international and local companies Degremont, Suez Environment, Thiess and Macquarie Capital Group.