Police officers in England and Wales have made arrests just to get people on to the DNA database, a retired police superintendent has claimed.
He told the Human Genetics Commission (HGC) this was the "norm". It wants new guidance for police to regulate when it is appropriate to take a sample of DNA.
Police chiefs have denied the claim, which they called "plainly wrong".
The database for England and Wales also holds some profiles of people arrested in Scotland and Northern Ireland.
Last year, according to Home Office figures, 17,614 offences were solved using a DNA match, including 83 killings and 184 rapes.The national DNA database in numbers
There are now about five million profiles on the national DNA database, a rise of 40% in two years.
The retired police superintendent, who is quoted but not named in a HGC report entitled Nothing to Hide, Nothing to Fear?, wrote to the advisory body expressing concerns that the way in which people were arrested appeared to have changed.
He wrote: "It is now the norm to arrest offenders for everything if there is a power to do so.
"It is apparently understood by serving police officers that one of the reasons, if not the reason, for the change in practice is so that the DNA of the offender can be obtained: samples can be obtained after arrest but not if there is a report for summons.
"It matters not, of course, whether the arrest leads to no action, a caution or a charge, because the DNA is kept on the database anyway."
But the Association of Chief Police Officers (Acpo) dismissed the claim as "plainly wrong".
The HGC report also said some groups featured disproportionately on the database - with young black men "very highly over-represented".
HGC chairman Professor Jonathan Montgomery said it had been transformed over the years from a database of offenders to a database of suspects.
Prof Montgomery told the BBC: "DNA evidence is important in the investigation of crime but it's far from clear that a database plays an effective role in that.
"We're calling for more research, more evidence in the contribution the database makes."
He told BBC Radio 4's Today programme there had not been a "public debate" concerning the database to establish "the correct balance between our private interests to privacy and our public interest in investigating crime".
Prof Montgomery called for "a discussion in Parliament about the purpose and limits of the database".
He said: "We should get it on a proper statutory footing and have independent governance. Only then will we be able to test whether the sort of things that were set to us, about possible deliberate arrest in order to take DNA samples were well-founded or not.
"We are just not in a position at the moment to find that out."
Currently everyone arrested for an offence that could lead to a criminal record has their DNA taken for the database, which is the largest of its kind in the world with five million samples.
The HGC's major review of the national database concluded that there was "very little concrete evidence" as to its usefulness in investigating crime.
The report also called for ministers to:
• Set out in law what DNA profiles can be used for
• Make abuse of records a criminal offence with strict penalties
• Create an independent advisory body with oversight powers to help make the database and its work more transparent; and
• Make police officers and everyone who comes into contact with crime scenes through their work have their profiles recorded as a condition of employment.
Former Acpo president Chris Fox told Today he had "never believed that innocent people should be recorded unnecessarily".
"However, police have always kept data about innocent people. It's the first chain of the intelligence route where you gather information about people who are doing odd things, and eventually something comes out of the which suggests it is not information, it is intelligence," he said.
But Mr Fox said the difference was that intelligence was "weeded and thrown away when it's no good", whereas DNA details were not.
He said he could see the temptation to arrest people in order to store their DNA details but did not think that had happened while he was the head of Acpo.
Shadow home office minister James Brokenshire, said: "For too long the government has had a policy of growing the DNA database for the sake of it regardless of guilt or innocence.
"Under Labour's surveillance state everyone is treated as a potential suspect."
Earlier this month the Home Office announced that the DNA of most innocent people arrested in England, Wales and Northern Ireland would not be kept for more than six years.
But it said police may be allowed to keep DNA from terrorism suspects, even if they are later freed or found not guilty.
A Home Office spokesman said they had set "the right threshold".
"DNA samples are taken on arrest for recordable offences carrying a prison sentence," he added.
"We know that the DNA database is a vital crime-fighting tool."
But Liberal Democrat home affairs spokesman Chris Huhne accused ministers of having a "cavalier attitude" towards DNA retention.
"Ministers make no distinction between innocence and guilt and as a result everyone is treated like a suspect," he said.
The European Court of Human Rights ruled last year that the database was illegal because it allowed police to indefinitely retain the profiles of people who had been arrested - but never actually charged or found guilty of a crime.
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