By Sean Curran
BBC Parliamentary Correspondent
Reforms could have unforeseen consequences, MPs have been told
The House of Commons' most senior official has warned that plans to clean up Parliament may have a "chilling effect" on MPs' freedom of speech.
Dr Malcolm Jack, the House Clerk, has said a bill to reform Parliament raises profound issues about the relationship between MPs and the courts.
It could see the words of MPs admitted as evidence in criminal proceedings for the first time, he told MPs.
The Parliamentary Standards Bill will be considered by MPs next week.
The bill, which will hand regulation of expenses to an external body - the Parliamentary Standards Authority - is being rushed through the Commons with a view to getting it on the statute book before MPs break up for their summer recess at the end of July.
It was introduced on Wednesday by Commons leader Harriet Harman in response to the expenses scandal.
In written evidence to the Justice Committee, Dr Jack - who acts as parliament's chief executive - stresses that he is not commenting on the merit of the bill's policy proposals.
But he said the bill "affects the established privileges of the House of Commons, thereby upsetting the essential comity between Parliament and the courts".
And he explained that parts of the bill would give judges the right to question proceedings in Parliament.
"It is not clear why this clause is in the Bill," he said.
"If its effect would be minimal, then it cannot really be needed. If it would have a significant effect, then the risk of litigation affecting the boundaries of jurisdiction between the courts and Parliament is substantial".
He adds that another section of the bill means that for the first time the words of MPs and House officials could be admitted as evidence in criminal proceedings.
"This could have a chilling effect on the freedom of speech of Members...and would hamper the ability of House officials to give advice to members," he warns.
In an unusual move, the Clerk will give evidence in person to the Justice Committee on Tuesday.
The Commons debate on the sections of the Bill mentioned in his evidence has been delayed until Wednesday.