The Metropolitan police are looking at allegations against former Liberal Democrat chief executive Lord Rennard and are considering if any criminal activity has taken place.
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The police were approached by Lib Dem officials following claims that Lord Rennard had behaved inappropriately towards women.
Channel 4 News understands that an influential Lib Dem has formally approached the Metropolitan police. The Lib Dem is acting as an intermediary for several women over claims of sexual impropriety against Lord Rennard. Superintendent Kate Halpin has been asked to look at the allegations.
A statement released by the Metropolitan police said: "The Metropolitan Police Service Specialist Investigations Command has been approached by officials in the Liberal Democrat Party and we are working with them to ascertain whether or not any criminal activity has taken place. We are keen to hear from anyone with information on this matter to contact us on 0208 721 4601."
Today, Liberal Democrat leader Nick Clegg denied failing to do enough when he heard rumours of allegations against Lord Rennard, saying the women involved had not made a "formal complaint".
On Sunday, Mr Clegg admitted that, in 2008, he had been aware of "indirect and non-specific concerns" over the behaviour of Lord Rennard - when the peer was warned that any such behaviour was "wholly unacceptable". Lord Rennard subsequently resigned as Liberal Democrat party chief executive on the grounds of ill-health.
Mr Clegg had said previously that the first he knew of the allegations was from a Channel 4 News investigation, broadcast last week. Lord Rennard strongly denies any wrongdoing.
Today one of the women interviewed anonymously last week publicly identified herself as Lib Dem activist Alison Goldsworthy.
She said in a statement: "I can confirm that I was the woman in the Channel 4 broadcast. I commend Channel 4, the Liberal Democrats and individuals within the party, for the efforts they have gone to maintain my anonymity over a period of years.
"I am disappointed people who I thought of as friends and other outlets have chosen not to respect that and as there is now an inevitability my name will be revealed, I have chosen to do so myself. I will be co-operating with the inquiries and have no further comment to make.”
Mr Clegg said on Monday, in an interview with Meridian, that the reason he had not taken stronger action when concerns were raised, was because the women making claims did not make specific allegations, and wanted to preserve their anonymity.
He said: "The women who at that point were expressing concerns about Lord Rennard's behaviour didn't want to be specific about the allegations, they wanted to keep their own privacy, their own anonymity if you like, intact.
"That's now changed, several years later, and now we can launch the investigations that I have announced - one into Lord Rennard's conduct - and remember he strenuously denies the allegations - and secondly into the general way the party handles these things, and I've confirmed last night that the investigation will be chaired by someone who is independent."
The one thing I probably can tell you without going through due process is that we screwed this up as a party - Tim Farron
That statement is at odds with the story told by one former Lib Dem activist, Alison Smith, who said she had tried to make a formal complaint. Ms Smith had reported her allegations, that Lord Rennard had acted inappropriately after inviting her and her friend back to his house, to the party's chief whip at the time, Paul Burstow, and spokesperson for women and equality, Jo Swinson.
Ms Smith told Channel 4 News: "It very quickly became quite Kafkaesque. They were saying, 'No one wants to make a formal complaint', and I was saying, 'I'll make a formal complaint,' and they were saying, 'That's a shame because no one wants to make a formal complaint'."
Difficult to pursue concerns
Mr Clegg also denied that he had known more in 2008, and that this had been the reason for Lord Rennard's resignation.
"He resigned for the reasons set out at the time," Mr Clegg said.
"What I have made clear is it was very difficult for us to pursue the concerns after he resigned since the women who had expressed anonymously some misgivings about him didn’t at that point want to turn that into a formal complaint, and what we need to look at is whether the format was alright for dealing with that.
"Now we know what the specific, formal, named allegations are because of the broadcast on Channel 4 and we can act, and that is what we will do, we will get to the bottom of what has actually happened."
Mr Hague was on Eastleigh on Monday morning, ahead of a crucial by-election on Thursday. He has since flown to Amsterdam for a meeting with Liberal Democrat leaders from other European countries.
Earlier on Thursday, Tim Farron, the Liberal Democrat president, admitted that the party had "screwed this up", and had failed in its "duty of care".
Speaking to BBC Radio 4, he said: "The one thing I probably can tell you without going through due process is that we screwed this up as a party.
"There are individuals out there who we had a duty of care towards and we did not fulfil that duty of care. That is something that we have to learn from, apologise for and make sure it never happens again."
He said he had heard a "general rumour" about Lord Rennard a year ago, but "no specifics".
"In my job you come across quite a lot of gossip and it is difficult to know how you separate out general unspecific gossip from specific complaints," he said.
"That is why we, as a party, with independent help and with real rigour, are now going to look at ourselves.
"My job as party president is not to defend the Liberal Democrats in this, in fact quite the opposite: it is to find out what happened and ensure these women get justice because I'm afraid they are the people who have been lost in... all the political furore."