Nick Clegg knew of Lord Rennard 'concerns' in 2008
Liberal Democrat leader Nick Clegg says he was made aware in 2008 of "indirect and non-specific concerns" about the party's then-chief executive.
Lord Rennard had been "warned" at the time but "categorically denied that he had behaved inappropriately and he continues to do so", Mr Clegg said.
The deputy PM said he had not known until last week about claims of alleged sexually inappropriate behaviour by the peer made by a number of women.
The party is to review the complaints.
The inquiry under the party's disciplinary procedures will also look at whether Lord Rennard stood down in 2009, after six years as chief executive, for reasons other than the health grounds stated at the time.
On Thursday and Friday, Channel 4 News broadcast allegations by four women of sexual impropriety by Lord Rennard in incidents spanning several years, the first in 2003.'Angry and outraged'
Some reports questioned if Mr Clegg, who was on holiday on Spain when the story surfaced, had known of the claims years ago.
Nick Clegg believes the timing of these allegations - not the allegations themselves - are an attempt to undermine his leadership and dent his party's prospects in a crucial by-election.
Hence the strong denial that he was involved in any cover up.
But tonight's statement was politically risky - because he had to say something about what he knew and when.
That meant admitting that he had heard of "non-specific concerns" about Lord Rennard's conduct five years ago.
But he insists that unless specific allegations were brought to his attention, there really was a limit to what he could do.
His critics will say he perhaps should have been more curious.
The Lib Dems say this issue is a sensitive one and should not be treated as a political football.
But in denying a cover up, it might be seen as something of an own goal by Nick Clegg not to take media questions on his statement tonight.
And Labour have certainly entered the political arena by calling for an independent inquiry.
In a statement on Sunday, Mr Clegg, who became party leader in 2007, said: "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."
Mr Clegg said the "concerns" had been put to Lord Rennard by his then-chief of staff Danny Alexander, who "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."
In his statement, Mr Clegg added: "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.
He said the Channel 4 broadcast showed that there were "legitimate concerns that issues raised with the party were not handled as well as they should have been" and the party review would examine this.
Ahead of Mr Clegg's statement, BBC political correspondent Iain Watson said: "I think privately he feels that this controversy isn't so much about Lord Rennard, there's an attempt to undermine him and his party leadership.
"Lib Dems themselves would admit that, in the run-up to a crucial by-election, these allegations haven't come at a good time."
Later on Sunday, Mr Alexander said in a statement: "The party has rightly set up inquiries into these matters and I will participate fully in those processes."'Total distortion'
Profile: Lord Rennard
Chris Rennard was born in Liverpool in 1960, and was an active Liberal Party member in his teens and later as chairman of the University Liberals and Social Democrats at Liverpool University.
He went on to become deputy chairman of the Liverpool Liberal Party, organising many of the party's successful election campaigns.
He was the most successful Liberal agent in the country while working in the Liverpool Mossley Hill constituency of David Alton (now Lord Alton of Liverpool), helping achieve a winning 14% swing against the Conservatives in 1983.
A key member of many Liberal/Alliance by-election campaign teams in the 80s, he also wrote party publications on campaigning.
In 1989, he was made an MBE, married Ann McTegart, and was appointed the Liberal Democrats' director of campaigns and elections.
In the 1997 general election, he oversaw the campaign which more than doubled the party's MPs - from 18 to 46. He also directed the 2001 and 2005 campaigns.
As party chief executive from 2003 to 2009, he also chaired the general election campaign from summer 2006 until he stood down.
Source: Liberal Democrats website
Two women told Channel 4 Lord Rennard had abused his position by inappropriately touching and propositioning them.
One of the women said she had spoken to two senior party figures about her claims, but said no action had been taken. Allegations from more women were broadcast on Friday.
"Gradually his hand started to rub the outside of my leg," one of the women - a very active member of the Lib Dems - told Channel 4.
"I thought at first he'd just brushed against me. Then I moved away and it happened again. And he moved closer - and I moved away again. And he moved closer, and he just kept brushing parts of me that I didn't want to be brushed."
Mr Clegg's former parliamentary aide, Jo Swinson, and now equalities minister, has said she "took action" after some women had confided in her, but she has not specified what form that action took.
The Mail on Sunday reported that one of the women who came forward to Channel 4 News had discussed the allegations with a friend on Facebook in January 2009.
"I just don't know how nick can know and not do anything.. :-( makes me very sad," she wrote, according to the paper.
Lord Rennard, who was also a key strategist and adviser to a succession of party leaders, said on Friday he was "deeply shocked" about the allegations and said they were a "total distortion" of his character.
The peer said he knew of no complaints against him in his 27 years working for the party, but he has temporarily stood aside from the Lib Dems' group in the Lords to avoid "embarrassment" to the party.