The families of two nine-year-old girls murdered in a Brighton park have vowed to pursue a retrial of the main suspect.

Relatives of Karen Hadaway and Nicola Fellows insist they will take civil action if a criminal case cannot be made against paedophile Russell Bishop.

Sussex Police are pursuing new lines of inquiry into the 1986 killings but do not yet know if they have enough fresh evidence to launch a retrial.

A spokesman said: "We are awaiting results of forensic and DNA tests."

Bishop, 38, was accused and acquitted of killing the nine-year-olds in 1986 after forensic evidence was called into doubt.

Under the double jeopardy law he could not be tried twice for the same offence. The 800-year-old law has now been revoked, leaving Bishop open to a second prosecution, although new evidence would be needed.

Bishop recently attempted to have himself sectioned under the Mental Health Act, which Ian Heffron, Nicola Fellows' uncle, believed was a ruse to avoid a retrial.

Bishop, a father-of-three, is being held at Wakefield Prison, West Yorkshire, for the kidnap, sexual assault and attempted murder of a seven-year-old girl in 1990. He was jailed for life.

Mr Heffron, 49, a former policeman, said "If the police cannot find enough evidence, we will go through the civil courts.

"My family are champing at the bit for a prosecution."

The families' efforts to bring the case to trial again may be hampered by the loss of key evidence.

A year ago it was revealed the BBC had lost some of Karen's clothing given to them in 1991.

It was passed to journalist Martin Bashir who was planning to make a documentary about the case for the Public Eye programme.

The programme was never made and no trace could be found of the clothes when the family tried to retrieve them last year in case they held vital DNA evidence.

Karen Hadaway's mother Michelle said: "I feel pretty angry about this."

Mr Heffron said no one from the BBC has apologised to the family for the loss of the clothes.

Mark Damazer, Controller of Radio 4, gave Mr Heffron assurances that changes would be made to ensure nothing of the kind ever happened again.

Mr Heffron said he was expecting a letter from Mr Damazer but it never came.

A spokesman for the BBC said: "It is a matter of regret that we didn't keep a proper set of records with regards to the items."