The police DNA database would still be illegal even if the government makes the changes it has proposed, according to the Equality and Human Rights Commission.

The government has consulted on changes to the rules about the DNA database after a European Court of Human Rights ruling in December 2008 found that elements of the system were unlawful.

Currently profiles of those charged with a crime but later cleared can be kept indefinitely on the database.

Under the government’s new proposals, even if someone has not been charged with committing a crime their DNA profile can be kept for up to 12 years, or indefinitely if they have been found guilty of any offence.

But the Equality and Human Rights Commission believes this proposal does not meet the European Court of Human Rights requirement for the government to have clear and justifiable reasons for holding on to DNA data from people who have not been convicted of a crime.

John Wadham, legal group director at the Commission, said people have a right to have their privacy protected.

"The proposed changes to the national DNA database are a step in the right direction, but we think there is no reason why the police should be allowed to keep anyone’s DNA profile indefinitely," he said.

"It would be sensible for the government to get this right now or it could face many more expensive legal challenges. Britain is at the cutting edge of how this technology is used in fighting crime, but it must be used lawfully."

The Commission said its recommendations are in line with the Council of Europe's guidance on the use of DNA in the criminal justice system, and were developed after taking legal advice from Michael Beloff QC.

The recomendation says a person’s DNA profile should only be kept for a limited period if they have been convicted of a serious crime and where destroying that information is likely to pose a risk to the public.

It also argues that it is unlawful to keep the DNA profile of a 10-year-old child arrested for a minor offence for the same length of time as an adult.

The Commission also calls into question the validity of the research used by the government to support its proposals, noting that the evidence has been criticised by other experts.