She will be replaced by Phil Bentley who will join on November 1 and assume the position of chief executive on December 12 following a short transition period.

McGregor-Smith has been a director of Mitie since December 2002 and has served as chief executive since April 2007.

Bentley’s last role was at Cable and Wireless Communications where he served as Group Chief Executive Officer.

He previously ran British Gas for seven years and has held a range of senior management and finance roles at Centrica and Diageo.

McGregor-Smith said: “It has been a real honour to serve on the Board of Mitie and in particular to hold the role of chief executive.

“I am delighted that we are now in a position to appoint a new chief executive for Mitie and I wish Phil a successful future with the group.

“I would like to say a big thank you to everyone at Mitie who has helped make this such an extraordinary place to work, in particular my management team.

“Thank you also to all the people who have worked for us since I joined, and to all of our other stakeholders, especially our clients, for their support over the past decade.”

Roger Matthews, Chairman of Mitie said: “Since becoming CEO, she has doubled revenue and profits, built a market–leading UK facilities management business, and been an inspiration to Mitie’s employees. I wish her every success for the future.

Bentley joins on November 1

“I am delighted that Phil Bentley is joining Mitie. He has proven CEO experience with an excellent track record of significantly enhancing shareholder value in services businesses.”

Bentley said: “Ruby has done a brilliant job building Mitie into the admired industry leader it is today.

“Although it is a challenging time for the sector, we have a strong platform from which I am certain we can now prosper.”

Mitie issued a profit warning last month while its shares are currently trading at 193p compared to a 12 month high of 335p.