The government must prevent police from storing the profiles of innocent people on the national DNA database, an influential group of experts has said. The Nuffield Council on Bioethics also recommended that ministers drop plans to extend police powers that would see DNA samples being taken from people suspected of minor offences such as littering or speeding.

"Innocent people are concerned about how their DNA might be used in future if it is kept on the national DNA database without their consent," said Sir Bob Hepple QC, chair of the council, which convened a group of lawyers, ethicists, geneticists and sociologists a year ago to study the ethical issues behind the use of biological information in police investigations.

The national DNA database has details of almost 4 million people and almost 400,000 profiles of biological samples (such as blood, semen, saliva or hair) left at crime scenes. It is updated every day and automatically compares the DNA profiles it receives with those from crime scenes. A Home Office report in 2006 said the database provided police with about 3,000 matches every month.

Under present laws, police can take DNA samples from anyone who has been arrested for recordable offences without asking permission. The profiles are permanently stored on the database, even if the person is later acquitted of all charges

"We're recommending that the police should only be permitted to keep the DNA of people who are convicted of a recordable offence," said Carole McCartney, director of the centre for criminal justice studies at the University of Leeds and one of the authors of the report, published today. She said exceptions could be made for people charged with violent or sexual offences.

But the Home Office said that maintaining records of people who were innocent at the time had helped solve crimes years later. "It is estimated that there are about 200,000 profiles on the database which would have been removed prior to a change in legislation in 2001," a spokesperson said. "From these, about 8,500 individuals have been matched with DNA taken from crime scenes, involving some 14,000 offences that include 114 murders, 55 attempted murders, 116 rapes, 68 other sexual offences, and a number of other serious crimes."

In March, the government asked for feedback on proposals to expand police powers to take DNA samples from people arrested of non-recordable offences. Dr McCartney said: "There's no actual evidence that's been provided that an increase in police powers would significantly improve the effectiveness of the DNA database."

The report also advised against a DNA database containing records of everyone, which some say would remove issues of discrimination which have seen some ethnic minorities over-represented. "This would be hugely expensive and would have only a small impact on public safety," it said.