Andrew Large, chairman of the Securities and Investments Board, will be challenged over claims that the SIB wastes resources by duplicating the activities of other regulators.
Among the questions Mr Large is likely to face will be that of why he has felt the need to go on so many official overseas visits rather than concentrating on dealing with regulatory issues at home.
One source said: "Alan Whicker would be green with envy at the amount of foreign travel Andrew Large has been involved in."
His appearance before the Treasury and Civil Service select committee tomorrow comes amid mounting concern among MPs over weaknesses in the present regulatory system.
Their questions follow a personal document sent to them last week by Phillip Thorpe, chief executive of the investment managers' watchdog, Imro.
Mr Thorpe was the co-author two years ago of the Large Report, a document then seen as heralding a long-awaited reorganisation of the SIB. He is known to have become highly disillusioned at the way many of the changes he pushed for have failed to come about.
A paper sent by Imro to MPs, first revealed in the Independent, was critical of the SIB's failure to regulate effectively.
But when he appeared before the select committee recently, Mr Thorpe dismayed MPs with his lacklustre performance.
He later claimed he had been unable to speak his mind fully. It was alleged that Mr Thorpe had been prevented by his chairman, Charles Nunneley, from speaking out on the issue.
Mr Nunneley has fiercely rejected this claim and another that the alleged gag came after an earlier conversation between him and the SIB's chairman.
The committee's chairman, Sir Tom Arnold, wrote to Mr Thorpe, asking him to clarify whether he had been gagged.
Mike O'Brien, a Labour MP on the committee, said: "We have received a letter from Mr Thorpe in answer to our inquiries as to whether he was prevented from giving evidence.
"He has confirmed that he did want to say things, but felt that as an employee of Imro he was told what the line was and he had to stand by it."Reuse content