The Confederation of British Industry (CBI), a leading business group, said it had fired Tony Danker as director general after an investigation into complaints of workplace misconduct, and replaced him with its former chief economist, Rain Newton-Smith.
The allegations that have been made over recent weeks about the CBI have been devastating," it said in a statement on Tuesday.
"While investigations continue into a number of these, it is already clear to all of us that there have been serious failings in how we have acted as an organisation. We must do better, and we must be better."
Mr Danker stepped aside in March while the CBI conducted a review into his behaviour.
The Guardian newspaper said a complaint was submitted in January by a female CBI employee and more allegations had been brought by other staff members subsequently.
On Tuesday, Mr Danker said he was “shocked” to learn he had been dismissed but also that he was "truly sorry" for making some people feel uncomfortable.
"I was... shocked to learn this morning that I had been dismissed from the CBI, instead of being invited to put my position forward as was originally confirmed," Mr Danker, who was director general of the business group, said on Twitter.
"Many of the allegations against me have been distorted, but I recognise that I unintentionally made a number of colleagues feel uncomfortable and I am truly sorry about that."
The CBI is one of Britain's best-known business organisations, representing the interests of many of the country's biggest companies to the government and more widely.
However, last week it halted its public events after further allegations – including one of rape at a staff party in 2019 – were reported in The Guardian.
The CBI said Mr Danker – who joined the CBI in November 2020 – was not the subject of the more recent allegations but that his conduct "fell short of that expected of the director general".
The CBI said three other employees were suspended pending further investigation into a number of ongoing allegations.
"The CBI is liaising with the police and has made clear its intention to cooperate fully with any police investigations," it said.
Ms Newton-Smith, who spent her early career as an economist at the Bank of England, left the CBI in March to join Barclays where she is Managing Director for Strategy and Policy, Sustainability and ESG.
"I want the CBI to be an organisation of which we can all be proud," she said.