PMQs: Cameron on Sir Cyril Smith child abuse claims
The prime minister said Greater Manchester Police had opened an investigation into allegations "from 1974 onwards" around the former MP Cyril Smith.
David Cameron said an interim report had some "extremely disturbing findings" and he called for people affected to make contact with the police.
Rochdale's current MP - Labour's Simon Danczuk - asked him for a full police investigation into allegations that the late Cyril Smith had been involved in child abuse, and allegations of a cover-up.
Sir Cyril, who died in 2010, had been an MP for the Liberal Party, and later the Liberal Democrats for 20 years.