Paraphrasing Lloyd George's "war is too serious to be left to generals", Mr Biffen said the conduct and investigation of MPs was "too serious to be left to parliamentarians, however experienced or distinguished".
Despite protests, the 17- member privileges committee dealt with the cases of Graham Riddick and David Tredinnick behind closed doors.
Both were judged to have fallen "below the standards of the House" in being prepared to accept £1,000 in return for tabling Commons questions when approach undercover by the Sunday Times.
Without a vote after a two-hour debate, MPs approved the committee's recommendations, suspending Mr Tredinnick, MP for Bosworth, for 20 sitting days and Mr Riddick, MP for Colne Valley, who quickly returned the cheque, for 10 days.
Mr Biffen, Leader of the House until he was sacked by Margaret Thatcher in 1987, said the committee should take evidence in public, membership should not be just MPs, and those under investigation should be allowed representation.
"Sooner or later these are matters that I do not think can be sensibly resolved in the arcane and historic practices of this chamber," he said.
Mr Benn said the investigation and the debate was "the most ghastly whitewash and cover-up of the real question": What were the "standards" expected of an MP? Were they those of an officer and a gentleman? "We have no standards." Standards should be a matter of law and applied to all MPs.
Dismissing the need for a vote, the Chesterfield MP said Messrs Tredinnick and Riddick had "done themselves about as much damage as any two MPs could have done".
The two MPs themselves made short, apologetic speeches at the start of the debate, and then, following precedent, left the chamber.
Mr Riddick stressed he had returned the cheque before he had "any idea it was a journalistic set-up". Mr Tredinnick told the House: "It is a matter of very considerable regret to me that I should have done anything that could have damaged the reputation of this House or caused concern in my constituency."
Tony Newton, Leader of the Commons and chairman of the privileges committee, said the reputation of the House had "inescapably" been damaged.
Though MPs finally agreed to the committee's recommendation, opinions on the appropriate sentence varied from Tory calls for a simple reprimand to the proposition of Kevin Barron, Labour MP for Rother Valley, that both MPs should be expelled to face the judgement of their electors.
Much heat was directed from the Conservative side at "elaborate entrapment" by the Sunday Times. Nigel Waterson, MP for Eastbourne, said that its reporters should have their lobby passes withdrawn for 20 days.
Ann Taylor, for Labour, said disciplining fellow MPs was "one of the most distasteful tasks" the House had to perform. But her colleague Dennis Skinner, MP for Bolsover, offered the ultimate solution: "One member, one job."Reuse content