Nick Clegg knew nothing of allegations that a senior Liberal Democrat official had molested a string of women until shortly before they were broadcast on television, according to business secretary Vince Cable.

Former Lib Dem chief executive Chris Rennard has been accused of groping the women, who include Bridget Harris, a former special adviser to Clegg, Alison Smith, a lecturer at Oxford University, and two unnamed Lib Dem MPs. He denies the allegations.

Emails written by one of the women suggest Clegg was informed of the claims in January 2009.

But Cable said this was untrue. Asked if he was aware of the claims, Cable said: "No absolutely not, and Nick Clegg has also said he wasn't aware of these allegations until they appeared on television last week. But they are serious allegations and we take them very seriously."

Two inquiries are to be conducted into the claims, one chaired by Lib Dem party president Tim Fallon, and another to be headed by the party's chief executive, Tim Gordon.

"The whole purpose of setting up these inquiries is to establish who said what to whom, and whether these allegations were properly pursued at the time," Cable said.

"It's very important that when complaints are made they are properly investigated and have an independent component to them, and that's what we are going to do."

Lord Rennard stepped down as chief executive in 2009, citing "health and family reasons", after 20 years of co-ordinating by-election campaigns for the party. But rumours about the scandals surrounding him have been circulating for several years.

Lord Rennard said he is "deeply shocked by and strongly disputes the allegations", which three of the women repeated on Channel 4 News on Thursday 21 February.

Cable insisted he was not aware of any suggestion that the rumours were the real reason behind Lord Rennard's decision to step down in 2009.

"As far as I'm concerned and I'm sure as far as Nick Clegg is concerned, this was an issue of him standing down because of health reasons, I'm absolutely sure."

Former party activist Alison Smith said Lord Rennard invited her and another female party member back to his house in London after they had dinner with him in 2007.

"He plonked himself between us and started moving his hands down our backs and places where they had absolutely no business being," she said. "It was both of us at the same time."

Another woman, an active Lib Dem member who has not been named, told Channel 4 how Lord Rennard "kept brushing parts of me that I didn't want to be brushed".

"Gradually his hand started to rub the outside of my leg," she said. "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."

Bridget Harris, a former special adviser to Clegg, said Lord Rennard touched her legs and knees inappropriately at a conference in Swansea in 2003. "It made me feel embarrassed and upset and disappointed," she said.

A third woman, who did not wish to be named, said the peer "shoved his hand down the back of my dress" when, as a 21-year-old party candidate, she posed for a photograph with him.

"It made me feel really humiliated and very undermined and very shameful," she said.

The women said they encountered a "Kafkaesque nightmare" after reporting the allegations to senior party figures including the party's chief whip, Paul Burstow, and its women's minister Jo Swinson.

Cable acknowledged that the women's complaints may not have been properly dealt with.

"It's obviously wrong if there are women who've made complaints and feel they haven't been dealt with, so we are now setting up a proper investigatory process. We want an independent element to that, to get to the bottom of it."

Swinson's original investigation uncovered a "serious pattern of behaviour" by Lord Rennard. But she told Smith she could not take the matter further as the women were not prepared to make a formal complaint.

An exchange of emails between one of the women in the Channel 4 investigation and a friend appears to cast doubt on Nick Clegg's claims not to have known of the allegations.

In the emails, the friend asks the women whether "the human octopus has struck again". In response, the alleged victim told her: "He is bricking it so much he has stopped... EVERYONE watches him now."

Discussing the way Swinson dealt with her complaints, the woman suggested Clegg had been informed of her claims.

"I just don't know how Nick can know and not do anything.. :-( Makes me very sad," she wrote.

In a separate development, a former female party official has provided details of conversations she had with Swinson, backed up by notes she made at the time.

Asked by Swinson at the Lib Dem conference in September 2008 whether Lord Rennard had ever behaved inappropriately towards her, she confirmed he had not, but said she could provide details of colleagues who had experienced such behaviour, including two MPS.

According to the official, Swinson confirmed that the two MPs were on her "list", but said only one of them had complained.

The official said she informed Swinson that journalists were investigating the claims, telling her that in their view, it was "not a story about Rennard but about Clegg and what he knew".

She said Swinson replied: "Yes, Nick is aware of that but we are pretty sure that none of the girls will talk."

She also claimed that during Swinson's investigation, Matthew Hanney, Clegg's political adviser, approached one of the victims to ask: "Do you mind if I speak to Nick about that?"