The public are to be asked whether the DNA database has expanded too much, amid concerns the innocent are discriminated against.

The UK holds 3.6 million DNA samples - the world's biggest database.

As well as criminals, samples are retained from those arrested but not convicted, and from victims and witnesses who give their consent.

The Nuffield Council on Bioethics will also hear views on the socioeconomic and ethnic make-up of the database.

Critics say the database is skewed, with opposition parties, civil liberties activists and even the inventor of DNA fingerprinting wanting major changes.

But the government and the database's supporters say it has revolutionised the fight against serious crime, catching many rapists and murderers who would otherwise have remained at large.

Professor Alec Jeffreys, from the University of Leicester, said hundreds of thousands of innocent people's DNA was now held.

He told BBC News: "The real concern I have in the UK is what I see as a sort of 'mission creep'.

"When the DNA database was initially established, it was to database DNA from criminals so if they re-offended, they could be picked up.

"Now hundreds of thousands of entirely innocent people are populating that database, people who have come to the police's attention, for example by being charged with a crime and subsequently released."

The scientist, who pioneered the DNA fingerprinting technique in the 1980s, said the samples were "skewed socio-economically and ethnically", adding: "My view is that that is discriminatory."

And he was concerned that samples taken for one purpose could be used for different purposes in the future.

Last week, Prime Minister Tony Blair revealed he had given his own DNA sample voluntarily in 1999 and said the maximum number of samples possible should be held on the database.

'Shoe rapist'

Police now get more than 3,500 DNA matches a month. In 2005/6 they got matches for 45,000 crimes, including 422 murders and 645 rapes.

It is understood a large number of serious crimes have been solved, in part, thanks to retained samples of those previously not convicted of an offence.

Tony Lake, chief constable of Lincolnshire and chairman of the National DNA Database Strategy Board, said he understood concerns.

But he told the BBC: "My real concern is that we have a database where we don't maximise the advantages as far as the public are concerned.

"The power of detecting these offences as far as the victims are concerned should never be underestimated."

He said it was not true that witnesses and victims automatically had their DNA put on the database, they had to volunteer in writing first. The process of giving a sample to help an investigation, and for the sample to be retained, is separate.

But once consent is given, it cannot be withdrawn, unlike in Scotland. Mr Lake said he was "personally uncomfortable" over this part of the system.

Nuffield Council chairman Professor Bob Hepple QC said they would consult the public over whether the fact that a disproportionate number of DNA samples were from young men or ethnic minorities meant there was a "potential for bias" in law enforcement.

The Home Office does not give precise figures on the ethnic make-up of the database, but admits that the number of samples from black males is disproportionate to the make-up of the UK population.

DNA database campaigner Henry Porter said the young were also present in disproportionate numbers.

"There are 24,000 under-18s who have committed no crime, not been cautioned, not even been in the court, whose DNA is held on this."

The council will also look at whether it would be fairer to include everyone on the database - something that the government has stopped short of proposing so far.

Prof Hepple said the central issue was whether the UK would "become instead of a nation of citizens, a nation of suspects".

Responding to the consultation

If you wish to respond to the consultation, please contact the LCCSA committee member Tom Epps, who is responsible for issues relating to Law Reform.  Alternatively, you can fill out the respondent?s form (Word document) and email it to: consultation@nuffieldbioethics.org

If you should prefer to respond by post or by fax, you may send your response, enclosing a completed respondent?s form, to:

Dr Carole McCartney
Nuffield Council on Bioethics
28 Bedford Square
London WC1B 3JS
UK
Fax: +44 (0)20 7637 1712