A double child murderer will not be placed on the sex offenders register because of a legal loophole, it has emerged.

Colin Pitchfork, 61, who raped and murdered 15-year-olds Lynda Mann and Dawn Ashworth in 1983 and 1986, is set to be freed from HMP Leyhill in Gloucestershire after serving 33 years in prison.

However, given that his crimes and sentencing were before 1997, he will not be placed on the sex offenders register, which has strict conditions aimed at monitoring offenders and stopping them from reoffending.

Instead, it is understood Pitchfork will be subject to regular meetings with a probation officer, lie detector tests and GPS tagging to stop any unsupervised contact with children.

The Telegraph understands the Ministry of Justice is not looking at closing the loophole to retrospectively place criminals whose crimes predate the 1997 law onto the sex offenders register. It favours placing conditions on those released on a case by case basis.

A government spokesman said: "Our thoughts remain with the families of Lynda Mann and Dawn Ashworth. Colin Pitchfork will be on licence for life and subject to supervision and conditions far stricter than the sex offenders register. If he breaches these, he faces being sent back to prison."

The case comes after Adam Stein, who kidnapped, raped and murdered six-year-old Collette Gallacher, was released from prison and also kept off the sex offenders register because of the same loophole.

Collette’s family have been campaigning to close the loophole so that other families do not see the killers and sexual abusers of their loved ones released without being on the register.

The Telegraph understands Stein will be on licence for the rest of his life.

Claire Holmes, Collette’s sister, has been campaigning against Stein’s release alongside her sister Lauren, saying: "When we found out, your brain starts thinking how many other people are out there that have just slipped back into normality? Or those that haven’t had the fight in them that we have to push for these extra stipulations.

"It is quite a scary loophole in the law that we’ve kind of stumbled across. How many other people have been affected and not not come forward?"

It is thought that the same conditions would apply to Timothy Morss and Brett Tyler, who killed and sexually assaulted nine-year-old Daniel Handley in 1994, if they were to be released.