Steve Corcoran has fallen on his sword after accounting problems were unearthed at the company’s International Division which operates across the Middle East.
The Finance Director of the International Division has also been suspended and other senior divisional management are the subject of further investigation.
A company statement said: “Given these events, Steve Corcoran believes it is appropriate that he resigns as Group Chief Executive.
“He will be stepping down from the board of Speedy Hire and will be leaving the company at a date to be finalised.
“He will remain with the business for a period to allow for continuity with customers, suppliers and employees and pending the appointment of a new Group Chief Executive.”
Problems with the accounts came to light following recent management changes at the International Division which accounts for 5% of group revenue.
Speedy said “information currently available suggests that certain control processes within the International Division have been repeatedly and deliberately circumvented.
“The issues are believed to affect a limited number of smaller contracts.”
The problems will knock an estimated £3m off full-year profits and have led to “constructive dialogue” with the firm’s lenders.
The news knocked more than 15% of the firm’s share price in early Friday trading.
Speedy has now engaged law firm Addleshaw Goddard LLP to carry out an independent investigation and forensic accountants are in the process of being appointed.
The firm said: “At this point no final conclusions can be drawn as to the timeframe nor the results of the above investigations.”
Corcoran joined Speedy back in 1987 and rose through the ranks before becoming chief executive in 2005.