He nominated Cyril Smith for a peerage after deciding allegations against him were "past history" – something that drew criticism from the Independent Inquiry into Child Sexual Abuse.
MPs were protected from prosecution in "a consistent pattern of failures to put the welfare of children above political status" – but inquiry finds no evidence of an organised paedophile ring.
Some of the victims were as young as 13. Police say there could be as many as 50 of them.
Angela Allen, who pleaded guilty to four child sex assaults, has been deemed no longer a significant risk to the public.
The mother-of-two was jailed in 2009.
Operational experts say the figure is a conservative estimate.
He compiled a handbook for other paedophiles.