Mitie, which offers security and cleaning services, competes with rivals like Serco and G4S and has a client base including the NHS, TfL and RBS.
It took a £50 million balance sheet writedown last month after admitting some of its accounting practices had been “less conservative” than some of its rivals’.
McGregor-Smith, dubbed the “prickly peer” for her testy relationship with the City, resigned last year as the company’s woes became apparent.
Bentley refused to be drawn on what he thought had gone wrong.
“You can only play what’s in front of you. You can’t go back and say if I’d been on the pitch this is what I’d have done because you weren’t there,” he said.
“I’m on the pitch now and we’ve got a great team and we’ve trying to move the ball up the pitch and play the game in front of us.”