The Confederation of British Industry said on Tuesday it had fired Tony Danker as director-general after an investigation into complaints of workplace misconduct and replaced him with 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.
"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."
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.
The CBI said three 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.
The CBI said the board wished to make clear that Danker was not the subject of the more recent allegations in the Guardian but it had determined that his conduct fell short of that expected of the director general.
Newton-Smith, a former Bank of England economist, left the CBI in March to join Barclays where she is Managing Director for Strategy and Policy, Sustainability and ESG.
After he was suspended, Danker expressed regret over his behaviour.
"It's been mortifying to hear that I have caused offence or anxiety to any colleague. It was completely unintentional, and I apologise profusely," he said in a statement.