Chris Huhne, the Liberal Democrat leadership candidate who has pledged to “stop the surveillance state in its tracks”, spent years on the board of a company that pioneered the use of mobile CCTV in Britain and profited from the sale of its shares.

The disclosure of Mr Huhne’s involvement with a supplier of speed cameras and surveillance equipment to the police may hurt his efforts to woo the wing of the party most concerned with civil rights. It comes at a critical point in the leadership race, with Mr Huhne fighting to keep pace with his rival Nick Clegg, the odds-on favourite.