Mr Clegg said all the current members of the parliamentary party who were around at the time had been questioned after the details of Sir Cyril's years of abuse of young boys were disclosed in the Commons in 2012, but none knew anything.
A search was also made of the party's surviving records following a request from solicitors representing one of the victims, but again, he said, it drew a blank.
The Lib Dems have been under pressure to explain what was known of Sir Cyril's activities following the serialisation by the Daily Mail of an investigation by Simon Danczuk, Labour MP for Rochdale, his former constituency.
Speaking on his weekly LBC radio phone-in, Mr Clegg said the party had sought to investigate when Mr Danczuk first raised Sir Cyril's "monstrous" abuse in the Commons two years ago.
He said that only a police investigation could now establish the truth of what happened. "I don't know why the police looked at this many, many decades ago and didn't pursue it then. If the police want look at it again, I think that would be right for the sake of the victims."