Two Derbyshire MPs have signed a letter raising concerns about how John Worboys - believed to be one of the UK's most prolific rapists - is to be freed from jail.
London cabbie Worboys was jailed indefinitely in 2009 with a minimum term of eight years.
A jury convicted the 51-year-old of 19 charges of drugging and sexually assaulting women, including raping one of them.
But since his conviction, police have received allegations from scores of other women spanning his 13-year career.
The black-cab driver is believed to have carried out more than 100 rapes and sexual assaults on women in London between 2002 and 2008.
A three-person panel has cleared him for release after serving less than a year for every woman he was convicted of attacking.
Chesterfield MP Toby Perkins and High Peak MP Ruth George are among 56 MPs who have signed a letter to David Lidington, the Secretary of State for Justice, to 'urgently investigate' how the decision has been managed.
The letter adds: "We would welcome an urgent investigation by your office into whether the victims of Mr Worboys were given an opportunity ahead of any parole hearing to make representations about his possible release.
"The decision to release Mr Worboys, even on strict licencing conditions, cannot be considered to have been made with a full and complete understanding of the impact of his many crimes without such information.
"It is vital that victims of such serious sexual assault have confidence not only in the prosecution of such crimes but also the subsequent management of those who are convicted of them too.
"We urge you to act urgently to ensure that in the case of Mr Worboy's and his entitlement to parole, his victims' voices are heard."
Yvonne Traynor, chief executive of Rape Crisis South London, described the time Worboys spent in prison as 'woefully short'.
She added: "It feels far too soon for this dangerous and manipulative perpetrator to be released into the public having served this woefully short time in prison.
"He may be free to live among us but the women he raped will never be totally free from his despicable actions."
In a statement, the parole board said: “We can confirm that a three-member panel of the parole board has directed the release of Mr Worboys, following an oral hearing.
"The arrangements for Mr Worboys' release will be managed by the Ministry of Justice."