Liberal Democrat peer Lord Rennard says he will not be apologising to women who accuse him of sexual harassment and has threatened legal action against the party after being suspended pending new disciplinary proceedings.
The party's chief executive said: "I do not believe that people should be forced to say what they know they should not say, or do not mean."
The peer has been suspended because of his refusal to say sorry.
The party's initial investigation concluded that the sexual harassment claims could not be proved beyond reasonable doubt, but said the women's evidence was credible and said they deserved an apology.
In a lengthy statement on Monday, Rennard said he "regrets" any hurt, embarrassment or upset they may have felt, but said he would not apologise, as this would leave him "defenceless in a future civil action".
Lord Rennard said that he was told last Wednesday by independent investigator Alistair Webster that the conclusion of his inquiry into the women's complaints was that there should be "no further action". But he said that the party had acted contrary to its own rules by refusing to give him a copy of the report.
After learning from Webster that the announcement of the report's conclusion would be accompanied by a statement saying that the women's evidence was credible and he should consider apologising, Lord Rennard contacted Lord Newby to warn him that this would cause "a major problem".
He said that he met Lord Newby and told him that he was resuming the Lib Dem whip, having voluntarily stepped aside during the inquiries, and the chief whip confirmed that he was readmitted.
"I have not spoken to, met with, or heard from Nick Clegg in 11 months," said Lord Rennard. "I would ask him, now that he has more knowledge of the facts, to ask for any threat to me to be withdrawn and to insist that I see the report, to which I am entitled, and to let me help him and my party again in future.
"I very much regret the wounds that have opened up within my party because many people have acted without being aware of the facts. I am particularly grateful to my friends and colleagues in the Liberal Democrat group in the House of Lords for much personal support.
"I would advise my friends in the party to let the matter rest, as it should have done, with the simple conclusion of the independent investigator that there should be no further action."
The announcement of his suspension has seen off a potential challenge to leader Nick Clegg's authority by preventing him taking up his seat alongside the party's other peers in the House of Lords, as he had planned.
Clegg has made clear that he is not willing to see Lord Rennard reinstated as a Lib Dem peer until he says sorry, telling the peer: "No apology, no whip."
In a statement released just minutes before Lord Rennard had been expected to re-enter the Upper House, the Liberal Democrats said: "Nick Clegg made clear last week, and again this morning, that it would be inappropriate for Lord Rennard to resume the Liberal Democrat whip unless he apologises. Lord Rennard has refused to do so.
"The regional parties committee, which oversees disciplinary procedures under the English party membership rules, today decided to suspend Lord Rennard's membership of the party pending a disciplinary procedure. As such, he cannot return to the Liberal Democrat group in the House of Lords.
"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 spokesman for Lord Rennard described the committee's decision as "extraordinary" and said the peer was "taking legal advice with a view to civil action against the party".
The spokesman added: "Lord Rennard would like proper consideration to be given to the statement that he made earlier today before there is any further action.
"He does not wish to see legal action between fellow Liberal Democrats, but his membership of the party matters more to him than anything apart from family and friends. Indeed he feels that the party is also his family.
"He believes that the suspension of his membership announced this morning should be lifted, that the party should now give him the report to which he is entitled and that Liberal Democrats should act in the best spirits of the party that he joined as a teenager."
Lib Dem president Tim Farron acknowledged that the allegations "were not dealt with properly" when they emerged in 2010.
"I think that Lord Rennard and the four women in question are owed an apology because rumours circulated, and indeed complaints have been made, and were allowed to fester," Mr Farron told BBC Radio 4's PM. "It was not fair to him that they were not dealt with properly at the time but it definitely wasn't fair to the women."
Mr Farron said it was "only right and proper" that Lord Rennard now apologise, saying his concern about exposing himself to a possible civil action was "a red herring".
"Two of the women in question have been very clear today and stated that they had absolutely no intention of pursuing a civil case against Lord Rennard and they simply wanted an apology," he said. " There is a conclusion to this which would be much less messy if only he would do what is perfectly reasonable."
Labour deputy leader Harriet Harman said Mr Clegg had made "an absolute pig's ear" of the issue.
She told Sky News: "I think it's been a terrible muddle. My sympathy is with those women who have complained and are left hanging."
Lib Dem peer Lord Greaves warned the party faced a massive internal crisis, and said it should set up a Northern Ireland-style "peace and reconciliation process" or face being badly damaged "for a generation".
"There is a huge chasm and each side is standing behind their own lines chucking grenades at the other and there is absolutely no dialogue going on," he told BBC2's Daily Politics.
Lib Dem international development minister Lynne Featherstone said Lord Rennard's expression of regret was not enough to bring matters to a conclusion.
"I am very sorry for Chris personally," said Ms Featherstone. "He is clearly in deep distress over this, but so are the women who have suffered over the years. On my part, I think an apology is in order and I think this is the inevitable ending to a procedure that has been protracted and to some extent unnecessary."