Deputy Prime Minister Nick Clegg has again insisted the Liberal Democrats had no knowledge of the child abuse scandal involving the party's former MP Sir Cyril Smith.
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.
"The whips' office in my party went and spoke to every single current member of the House of Lords and the House of Commons who was around at the time of Cyril Smith and said 'Do you know anything?'. No one said they did," he said.
"We have even scoured what little documentation there is from that time. There simply is no documentation. We went to some warehouse outside London where there is documentation stretching back to when the party started. We have gone through it all."
Mr Clegg said that much of the abuse related to the period before the Lib Dems were formed in 1989 from the merger of the Liberal Party and the Social Democratic Party. Sir Cyril - who died in 2008 - stood down as an MP in 1992.
The Deputy Prime Minister confirmed that former Liberal leader Lord Steel, who headed the party for much of the period that Sir Cyril was in Parliament, was among those questioned by the whips.
"David Steel can speak for himself," he said.
He said that only a police investigation could now establish the truth of what happened and why no action was taken against Sir Cyril during his lifetime.
"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 the right thing, for the sake of the victims," he said.
Mr Clegg indicated that it would not be possible to strip Sir Cyril of his knighthood posthumously, as some are now demanding.
"My understanding is that these honours die when the person dies, so to speak, so there is not something there to be taken away now," he said.
Mr Danczuk said it was "inconceivable" that Mr Clegg had been unaware of the rumours regarding Sir Cyril's activities.
"He's far too defensive on this and I think it would help if the Liberal Democrats and Nick Clegg came out and said they were going to have an internal investigation, a thorough investigation, because, if not, I think it's right and proper that we have some sort of judicial review," he told LBC.
Calls for the Lib Dems to stage an inquiry were backed by lawyers representing Sir Cyril's victims.
Alan Collins, abuse lawyer at Slater and Gordon who represent six of the alleged victims, said: "In light of the fact that allegations appeared in print in 1979 and it has been reported that colleagues heard 'whispers', the party owes it to the victims, and its members, to establish who knew what, and when, and the way to do that is through an independent investigation."