Brown bans expenses rule-breakers from standing at next election
After addressing a meeting of Labour's ruling National Executive Committee, the Prime Minister also promised "major changes" in the system of MPs' expenses.
He said that, from today, the expenses of every MP going back four years would be examined.
Mr Brown added: "If they are found to have broken the rules, then action will be taken."
He refused to comment on Commons Speaker Michael Martin's intention to announce his resignation this afternoon.
Mr Brown, speaking after a meeting of Labour's national executive which discussed the expenses crisis, said it had unanimously decided that "no candidate, no Member of Parliament will stand for the Labour Party at the next election" if they had "defied" the rules on expenses.
The Prime Minister would not be drawn on the future of the Speaker, saying "it is not for the Prime Minister to tell the Speaker what to do".
But Mr Brown will hold his regular monthly press conference in No 10 at 5.30pm, when he will be bombarded with questions about Mr Martin's resignation.
Tory former shadow home secretary David Davis, who also signed the motion, said it was time for the Commons to find "a new voice" but ruled out standing for the post himself.
Mr Davis said: "I commend the Speaker for putting Parliament before his own career.
"And I would stress that the need for a new speaker is more a reflection on the needs of Parliament than a reflection on him."