Nick Clegg has said he is "outraged" by allegations that Liberal Democrats covered up sex claims against a former senior figure in the party.
The Deputy Prime Minister flew back from holiday into a storm surrounding the allegations against Lord Rennard, one of the Lib Dems' most powerful figures, and the way these allegations have been handled.
Clegg rejected claims that he knew about a string of reports of inappropriate sexual conduct against Rennard, the Lib Dems' former chief executive.
In a sign of growing anxiety within the party about the potential effect of the claims, the Lib Dem leader issued a strongly worded statement.
But he admitted that "non-specific concerns" about Rennard reached him as long ago as 2008.
Rennard, who quit his post for health reasons in 2009, has vehemently denied the allegations against him.
"The allegations made on Channel 4 concerning Lord Rennard were extremely serious and distressing to the women involved. It is critical they are investigated thoroughly and dealt with properly and they will be," said Clegg.
"But I would like to make one thing crystal clear. I did not know about these allegations until Channel 4 informed the party of them shortly before they were broadcast. I have spoken to one of the women in the broadcast who I respect and admire and who confirmed that she had never raised the issue with me.
"I am angry and outraged at the suggestion that I would not have acted if these allegations had been put to me. Indeed, when indirect and non-specific concerns about Chris Rennard's conduct reached my office in 2008, we acted to deal with them.
"My chief of staff at the time, Danny Alexander, put these concerns to Chris Rennard and warned him that any such behaviour was wholly unacceptable. Chris Rennard categorically denied that he had behaved inappropriately and he continues to do so. He subsequently resigned as chief executive on health grounds.
"As my office only received concerns indirectly and anonymously, as those involved understandably wanted to maintain their privacy, there was a limit to how we could take this matter forward following Chris Rennard's resignation. It is incorrect to state that there was any other separate inquiry by my office or anybody in it.
"I recognise from the Channel 4 broadcast that there are legitimate concerns that issues raised with the party were not handled as well as they should have been. In particular the suggestion that a complaint was made but was not dealt with as a formal complaint.
"I am therefore determined that we carry out a thorough investigation into our procedures and how we applied them at the time to ensure we have a full and clear picture of what happened and the lessons that we need to learn. This review will be independently chaired.
"A separate investigation into the specific allegations about Lord Rennard will take place under our disciplinary procedure . It is essential that this is carried out with due process and for that reason I cannot provide a running commentary on it. But I am absolutely determined that both these investigations will be carried out thoroughly and comprehensively. These investigations may well reveal flawed procedures, and clearly the women concerned feel they were not properly listened to. But I totally reject the insidious suggestion that my office or I are responsible in any way for a deliberate cover up.
"The full truth of what happened and what failed to happen and who said what to whom will be revealed by these investigations. But in the meantime, I will not stand by and allow my party to be subject to a show trial of innuendo, half-truths and slurs. The important thing is that we respect the women who have come forward and do everything to get to the truth. That is what will now happen."