The policeman in charge of the Sally Anne Bowman murder inquiry today called for the national DNA register to be made compulsory.

Detective Superintendent Stuart Cundy urged the adoption of the register after Mark Dixie was found guilty of killing the 18-year-old model.

Dixie was the second high-profile suspect in as many days to have been caught and convicted because his DNA had been collected over a minor offence.

Yesterday, Steve Wright was found guilty of murdering five women who worked as prostitutes in Ipswich.

He was arrested after his DNA – which was on the police database following a conviction for petty theft five years ago - was found on three of the victims.

Cundy said having the DNA of everyone in Britain on file would speed up arrests and cut down on further offending. Bowman's mother, Linda, has also called for a national register.

"If there was a DNA register, we would have known who killed Sally Anne [on the day her body was found]," he said.

In a statement today, the Home Office said the database was "an invaluable police tool", contributing 3,500 police leads a month, but that there were no plans to make it compulsory.

"To do so would raise significant practical and ethical issues," the statement added.

Dixie was arrested in June 2006 - nine months after Bowman's murder - within hours of his DNA being put on national police computers following his arrest for a minor offence.

Detectives believe it could have taken up to two years for him to be tracked down had he not been arrested following a minor scuffle at the Surrey pub where he was working.

Since 2004, police have been given powers to take DNA swabs from anyone arrested and taken to a police station.

The national police register contains 4.2m records, which are kept for the duration of their subject's life. Records are rarely deleted, even if a person is never charged with an offence.

Up to 500,000 people who have profiles on the database have not been convicted or cautioned for a crime. That number includes profiles of 100,000 children, the Liberty pressure group said.

Hugh Whittall, the director of the Nuffield Council on Bioethics, said there was no data to suggest a significant increase in the number of solved crimes because of the inclusion of people who had not been convicted of serious offences on the database.

Whittall said a universal database raised serious issues of cost, privacy and "the relationship between the state and the individual".

"The proportionality of that is simply out of kilter," he added.

Dixie had 16 previous convictions in Britain, but in each case had been arrested before DNA was routinely taken from suspects.

He burst into tears when his DNA was taken in 2006, but did not attempt to flee when he was released on police bail.

"He probably thought he had got away with it when he did not hear anything immediately," Cundy said.

Around 1,700 men in the Croydon area gave their DNA voluntarily to be eliminated from the Bowman investigation.

Police were also working through a list of 22,500 local suspects before widening their search to other parts of London when Dixie was identified.

After Dixie's arrest for murder, his DNA profile was also sent to Australia, where officers in Perth found a match for an unsolved 1998 attack on a Thai student.