Companies likely to tender for work on the multibillion pound identity card scheme were yesterday sent a formal warning from the Tories that a Conservative government would cancel the project.

David Davis, the shadow home secretary, also wrote to the government urging it to take the risks of future cancellation under a Conservative administration into account in the procurement for the scheme. In a letter to Sir Gus O'Donnell, the cabinet secretary, Mr Davis said the Tories would cancel the scheme "immediately on our being elected to government".