The Driver and Vehicle Licensing Agency (DVLA) has made more than £6 million last year selling access to the names and addresses of motorists to private sector companies such as wheel clamper, bailiffs and debt collection agencies.

This is a 27% increase on what the DVLA earned the year before from selling ownership details. The DVLA currently charges an administration fee of £2.50 to anyone who can demonstrate "reasonable cause" to receive the information from the vehicle database.

Once the request is approved a company can submit a car registration number to find out the name and address of the vehicle's owner.

One of the issues is that "reasonable cause" is not defined in the law but a DVLA spokesman said it takes its duty under the Data Protection Act to protect the privacy of motorists "very seriously" and said each request is considered on merit.

He said: "Applicants must provide as much detail as possible to support their request. Insufficient information or use of data outside the 'reasonable cause' provisions will mean refusal of the application. Members of the public are subject to more stringent checks and must provide supporting evidence such as police reports and their insurance details."