Lib Dem leader Nick Clegg is committing his party to abolishing prison sentences for the possession of drugs, including heroin and cocaine.
Cable said he had no knowledge of the 'reprehensible' polls leaked by Lord Oakeshott on Nick Clegg's leadership.
The Liberal Democrat peer is taking a leave of absence from the Lords and resigning from the party, but is he the 'busted flush' some think?
Three of the four women who accused former Lib Dem chief executive Lord Rennard of harassment have called for the peer to be "kicked out" of the party.
Bridget Harris, a Lib Dem activist, has welcomed Lord Rennard's apology, but said his position within the Liberal Democrats was untenable.
"The real question here is, 'Should the Lib Dems accept him back on the benches in the House of Lords?' And I don't think the answer to that is yes", Ms Harris told BBC News.
Another activist who made the claims, Susan Gaszczak, said, "We really have got to draw a line under this. The only way to do that is actually to say, 'Lord Rennard, it's time to go.'"
A third woman, former Welsh Assembly candidate Alison Goldsworthy, told Channel 4 News the apology was a start, but stressed she thought Lord Rennard should be expelled from the Lib Dems.
One of the four female Lib Dem activists who accused Lord Rennard of harassment has said she has mixed feelings after receiving a written apology from the peer.
Former Welsh assembly candidate Alison Goldsworthy told Channel 4 News:
I am relieved that some acceptance has now started to come forward from Chris Rennard that what he did was not okay but very frustrated that I have had to spend the last 15 months talking about things that are really very private and quite intimate to me to be able to achieve it.
If he had accepted and offered this apology up 15 months ago then things may be very different.
Ms Goldsworthy said "the fact that Chris Rennard has now accepted that his behaviour was untoward" meant Lib Dem leader Nick Clegg should expel him from the party.
The Liberal Democrats have confirmed appeals from both sides are ongoing following the investigation into the harassment claims against Lord Rennard.
A statement issued in response to reports of the peer's written apology said:
– Liberal Democrat spokesperson
An appeal has been submitted by three of the original complainants against the outcome of Alistair Webster's investigation.
Separately, an appeal has been submitted by Lord Rennard against the disciplinary process for bringing the party into disrepute by his failure to apologise, and his conduct after the publication of Webster's conclusions.
Both appeals will be considered by the English Appeals Panel in accordance with the rules of the party. We cannot comment further on any aspect of that process while it is ongoing.
Former Liberal Democrat chief executive Lord Rennard has issued a written apology to four party activists who accused him of harassing them.
The peer said "he may well have encroached upon personal space" and added he would like to "apologise sincerely for any such intrusion," which he said "would have been inadvertent".
Lord Rennard wrote that he was issuing the apology after receiving the report by Alistair Webster QC, who conducted an independent investigation into the allegations and the party's handling of them.
Mr Webster found no evidence to act against Lord Rennard but recommended he consider apologising.
A statement issued by his lawyer said: "Lord Rennard wishes to achieve closure of the contentious issues that have been in the public domain for the last 14 months by expressing his apologies to Susan Gaszczak, Alison Goldsworthy, Bridget Harris and Alison Smith."
Nick Clegg has sent out a defiant message that he will "fight back" as he is pictured in a "political storm" on the front page of Sheffield's The Star newspaper.
The Star tweeted a preview of the dramatic front page a day before it hits the news stands:
Read the exclusive interview with Nick Clegg on his 'tough week' and his election reaction only in tomorrow's Star http://t.co/1QbK0ZTAEz
Mr Clegg has faced a failed attempt to oust him as Liberal Democrat leader in the aftermath of the party's dreadful showings in the recent local and European elections, amid doubts he can retain his own Sheffield Hallam seat at next year's election.
By Chris Ship, ITV News Deputy Political Editor
Within the Liberal Democrats, Nick Clegg personally is pretty safe. His chief potential rivals - Vince Cable, Tim Farron and perhaps Danny Alexander - have all had to row in behind Mr Clegg and say how much they support him.
Where does it leave the Liberal Democrats in the country after the terrible showing in the local and European elections last week?
I don't think they are in a very good place at all.
David Cameron has said that he only judges Vince Cable by "the results he delivers", as he does all his ministers.
The Prime Minister was speaking in the wake of a failed leadership coup against his Liberal Democrat Deputy PM Nick Clegg.
Liberal Democrat leader Nick Clegg has said that he will not sack his Business Secretary after insisting that he had no part in a failed plot to oust him.
The Deputy Prime Minister said the Business Secretary was fully supportive of his leadership and insisted he did not believe "for a second" the Cabinet minister had been behind the plot to force him out of the party's top job.
During his regular Call Clegg show on LBC he said: "He was absolutely not aware of polls elsewhere. He has made it very, very clear that he, for instance, didn't want any questions about leadership in the poll which he did have some control over in his own constituency.
Nick Clegg has played down suggestions that Vince Cable knew about a controversial poll commissioned by Lord Oakeshott in the Deputy Prime Minister's constituency.
The peer, who has now resigned from the Liberal Democrats, privately commissioned surveys in several constituencies that showed a collapse in support for the party since 2010.
But Mr Clegg insisted the Business Secretary, once seen as an ally of Lord Oakeshott, was unaware of a survey in the Lib Dem leader's Sheffield Hallam seat.
"Vince Cable clearly didn't know a thing about a poll being conducted in Sheffield," the Deputy Prime Minister told BBC Radio Sheffield.
Vince Cable has insisted he has remained loyal to Nick Clegg, saying "there was no disloyalty whatever".
Speaking to the BBC in China the Business Secretary denied he was involved in secret polls undermining Mr Clegg's leadership, and said he wanted to make it "absolutely clear" he was backing the Deputy Prime Minister.
He added: "People are putting round the story that there is some division on that, there is not. I made it absolutely clear from the beginning of this week that there is absolutely no leadership issue."
He said that although "lots of polls" were carried out, he "knew nothing" about the ones that Lord Oakeshott ran, which indicated the party's general election performance would improve were Mr Clegg to resign.
Lord Oakeshott has since resigned from the Liberal Democrat party.