Plant hire group Speedy Hire has appointed a new chief executive after the previous chief executive resigned following the discovery of alleged accounting irregularities.Speedy Hire said it had promoted its Chief Operating Officer Mark Rogerson to the top role following the departure of Steve Corcoran.Corcoran said in November that he felt it was appropriate to step down after it emerged that a number of accounting balances in the international division had been mis-stated.Speedy Hire suspended the division's finance director and launched an investigation. Rogerson was appointed to the board in December and joined Speedy from Costain Group where he was Managing Director of the construction and engineering group's natural resources division.Before working at Costain, he spent eight years at support service group Serco in various senior leadership roles.Corcoran, who was with the group for 25 years, will step down from the board and leave the group with effect from today.Chairman Ishbel Macpherson said: "The board and I are delighted that someone of Mark's calibre and drive has taken up the challenge to lead Speedy at this exciting point in its development."Shares in the group, which dropped by a fifth following news of the alleged accounting irregularities, fell 3.46% to 62.75p at 10:41 on Monday.PW