British Deputy Prime Minister Nick Clegg's Liberal Democrat party on Monday suspended a parliamentarian who refused to apologise over sexual harassment claims.

Chris Rennard, the party's former chief executive who now sits in the House of Lords, the upper chamber of parliament, now faces investigation for bringing the party into disrepute.

A row over the case had threatened to undermine Clegg's authority as leader of the party, which is in coalition with Prime Minister David Cameron's Conservatives.

Four female party activists made complaints of sexual harassment against Lord Rennard, 53, causing him to resign the "party whip", or his affiliation to the Lib Dems, in 2013.

An independent investigation published last week found that the sex claims could not be proved to a required standard, but recommended that Rennard should apologise.

Rennard had been due to return to the House of Lords on Monday, in a direct challenge to the authority of Clegg, who said the peer should say sorry first.

"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," a party spokesman said.

The Lib Dem's main decision-making body "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," the spokesman said.

Rennard "will now be investigated for bringing the party into disrepute on the grounds of his failure to apologise," added the spokesman.

The portly Rennard was for a long time a crucial figure in the Liberal Democrats' electoral operation, building them up over the years from third-placed laggards to members of the government.

He resigned as chief executive of the party in 2009 due to poor health.

Rennard issued a statement on Monday again denying the allegations and saying he was "certainly too ill" to take up his place in the House of Lords on Monday.

He said of his alleged victims that "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."

The scandal has dogged Clegg and the Liberal Democrats for months, with claim and counter-claim about when the party leadership knew of the Rennard allegations.

In February 2013, Clegg admitted "very serious mistakes" in handling the issue.

The Lib Dems have had their share of scandals, including an alcoholic former leader, an MP's affair with a rent boy, and the jailing of former energy minister Chris Huhne and his ex-wife last year for obstructing justice following their bitter divorce.