David Lawther has stood down as chief executive of ISG just weeks after the fit-out specialist agreed to a takeover from US private equity firm Cathexis.
It is understood that Mr Lawther will leave the company with immediate effect after 10 years at the helm.
ISG has appointed Paul Cossell as its new CEO.
Mr Cossell has been at the firm for 20 years and was most recently managing director of its fit-out and engineering services arm.
The ISG board told shareholders to accept a takeover bid from Cathexis in February after a two-month battle for control of the group.
The 171p per share offer valued the company at around £85m.
It is understood that the change of ownership played a part in Mr Lawther’s decision to leave.
Mr Lawther said: “I am pleased to leave the company at a time when it faces a new and exciting future as a private entity.
“Paul has an impressive track record of growing profitable businesses in ISG and I wish him the very best in his new role. I have every confidence that the company will go from strength to strength under his leadership.”
Mr Cossell said: “I feel incredibly privileged to be appointed CEO of this great business as we embark upon the next stage of our journey under private ownership. We are by nature ambitious and innovative at ISG, and under our new ownership we have the opportunity for significant growth.
“We will build on our market-leading credentials to be recognised as the best brand in the construction sector, offering an unbeatable customer experience.
“I’d like to take this opportunity to thank David for the great contribution he has made to ISG after 15 years with the business and wish him the very best for the future.”