The taxpayer is facing a £150 million bill following the Home Office's decision to give Capita the contract to vet people working with children and the vulnerable.

Officials took the cheapest quote for providing the service, but have ended up paying more than the most expensive tender submitted for the Criminal Records Bureau contract.

Capita's bid claimed it could deal with three million applications over ten years for £250 million.

However, because of poor planning by the Home Office, the cost to the taxpayer will be £400 million.

Jon Trickett, a Labour member of the Commons public accounts committee, said: "It had to be one of the most incompetently let contracts this committee has seen, certainly since I have been on it," he said.