Pitchfork’s release came after bids to keep him in jail failed.
Barbara Ashworth, whose daughter Dawn, 15, was murdered, said: “He should never be walking the streets again.
“He should have been locked away for life without parole.”
Pitchfork, now 61, killed Dawn and Lynda Mann, also 15, in Leicestershire in the 1980s. Both were raped and strangled. The first killer convicted on DNA evidence, he was jailed in 1988 with a 30-year minimum life term, later cut by two years.
The Parole Board last month approved his bid for freedom saying he no longer posed a threat. Victims’ families, MPs and ex-police officers called for a rethink. But the board rejected a challenge by Justice Secretary Robert Buckland.
Lynda’s sister Rebecca Eastwood said yesterday: “I just can’t get my head around it.”
And Alberto Costa, Tory MP for South Leics, warned: “In my view, Pitchfork still presents a very real danger to the public.”
Now known as David Thorpe, Pitchfork is banned from going near victims’ relatives and his access to the internet is limited.
He faces lie detector tests and has to wear a tag in what the Ministry of Justice calls the “strictest” conditions yet set. The MoJ said: “If he breaches these conditions, he faces an immediate return to prison.”
Mr Costa welcomed a Government review of the Parole Board saying in cases like this “life should simply mean life”.
Pitchfork, a former baker, killed Lynda in Narborough in 1983. Three years later, he attacked Dawn in nearby Enderby. After he was jailed for life, Lord Lane, the Lord Chief Justice, said: “I doubt if he should ever be released.”