The Prime Minister has been challenged in the House of Commons about the case of paedophile Stephen Ayre.
Stephen Ayre was told he will spend the rest of his life behind bars
Ayre, 44, of Bingley Road, Shipley, was jailed for life in April after he raped a 10-year-old boy near Saltaire while out on licence for murder.
The Tory MP for Shipley, Philip Davies, said the case proved more prisons were needed to stop dangerous offenders being released early.
Tony Blair said prisoners deemed a risk could now be jailed indefinitely.
Mr Davies said: "Stephen Ayre was a convicted murderer who was released early and went on and abducted and raped a 10-year-old boy in my constituency.
"Will the Prime Minister agree with me that the way to tackle overcrowding in prisons is not to release dangerous people out early onto our streets, but to build more prisons so that prisoners can serve their sentences in full?"
Mr Blair replied: "As a result of the Criminal Justice Act 2003, now such people can be given indeterminate sentences, in which case they are not automatically parolled but will only be released when they are no longer a danger to the community.
"It is precisely because of cases like the one he mentioned that we introduced this provision and I think I am right in saying that there are almost a thousand people that have been subject to them."