The mother of murdered teenager Sally Anne Bowman has backed the Prime Minister over Labour’s controversial policy of keeping innocent people’s DNA on a national database.

Mark Dixie, who raped 18-year-old Sally Anne as she lay dead or dying outside her home in 2005, was only caught after getting involved in a pub brawl and having his DNA taken.

Despite not being convicted for the fight, his DNA was analysed and connected to the murder of Sally Anne, for which he was jailed for at least 34 years in 2008.

Mrs Bowman joined Gordon Brown on the campaign trail as he attacked Conservative plans to remove innocent people from the database - a move she says prevented Sally Anne’s boyfriend from being wrongly charged with the crime.

Mr Brown said: “Linda Bowman is a remarkable and brave woman who has suffered the most unspeakable tragedy yet still manages to be a compassionate campaigner for good.

“As Mrs Bowman says, the use of DNA helps the police put the most dangerous criminals behind bars but can also exonerate the innocent.”

But the claims have been branded “election fever” by civil liberties groups who point out Mark Dixie’s DNA was never held as an ‘innocent’ on the database.

Shami Chakrabarti, director of Liberty, said while DNA taken on arrest should be checked against unsolved crimes, it was an entirely different matter to stockpile the DNA of innocents for years on end.

Dixie, who pleaded not guilty to murder, told the Old Bailey he had stumbled across Sally Anne’s body outside her home and had sex with her before realising she was dead in September 2005.

The court heard the chef, who was branded “repulsive” by Judge Gerald Gordon, had a 20-year history of sexual violence before he was caged for the teenager's murder.

Labour has promised to keep the DNA profiles of anyone arrested but not convicted for six years, while the Tories would remove DNA information of anyone not convicted.