His statement last night came hours after the peer at the centre of sexual harassment allegations was suspended from the LibDems pending a disciplinary inquiry.
His suspension, for failing to apologise to four women complainants over claims of inappropriate touching, was announced one minute before the House of Lords was due to sit and the peer was expected on the red benches.
In a statement earlier in the day Lord Rennard, a campaign guru who helped his party to success at three general elections, said he was too distressed and ill to make an appearance in the Upper Chamber.
The former party chief executive repeated his firm denial of having done anything intended to distress the four complainants.
The 53-year-old said he "regrets" any hurt, embarrassment or upset the women may have felt but stressed he would not apologise as this would leave him "defenceless in a future civil action".
Last night Lord Rennard upped the ante. His spokesman said he believed his suspension should be lifted, the party should give him a report by Alistair Webster, QC, which looked into the claims, and LibDems should act in the best interests of the party.
The spokesman said: "In the light of the extraordinary decision by the English Regional Parties Committee Lord Rennard is having to take legal advice with a view to civil action against the party."
Lynne Featherstone, the LibDem International Development Minister, said his expression of regret was not enough.
Bridget Harris, one of the complainants and a former aide to LibDem leader Nick Clegg, said: "Nick felt deeply responsible that all of this happened and, on paper, it felt like there was very little the leadership could do. But actually, as it has turned out today, there is something we can do. We can send a strong message that this kind of behaviour is not tolerated."
Yesterday, the Deputy Prime Minister said he was not willing to see Lord Rennard reinstated as a LibDem peer until he said sorry.
With a showdown expected in the Lords, the party said its disciplinary committee had decided to suspend Lord Rennard's membership pending a hearing and he could not return to the Liberal Democrat group in the Lords.
In a statement, the committee said: "Lord Rennard will now be investigated for bringing the party into disrepute on the grounds of his failure to apologise, as recommended by Alistair Webster, QC."
A source said the "ultimate sanction" if the hearing found against the peer was expulsion.
Mr Webster concluded there should be no further action against the lord but suggested the women's evidence was credible and the peer should consider an apology.
On learning of his suspension, the peer said in a statement: "It is impossible to describe how enormously distressed I am by this situation and I am certainly too ill to attend the House of Lords today."
Lord Rennard referred to health problems, including depression.
He said: "Courtesy has always been an essential part of my moral compass. If ever I have hurt, embarrassed or upset anyone, then it would never have been my intention and, of course, I regret that they may have felt any hurt, embarrassment or upset.
"But for the reasons given, I will not offer an apology to the four women complainants. I do not believe that people should be forced to say what they know they should not say or do not mean."
LibDem peer Lord Greaves warned: "There is a huge chasm and each side is standing behind their own lines chucking grenades at the other."