LONDON — After falling for an embarrassing media sting, two British former foreign secretaries were on Monday facing investigations into whether they broke rules prohibiting lawmakers from trading influence for money.

Malcolm Rifkind, a member of the governing Conservative Party and head of a parliamentary panel that oversees British intelligence agencies, and Jack Straw, of the opposition Labour Party, were both caught by an undercover reporter posing as the representative of a Hong Kong-based company that purportedly sought to hire them.

The episode reopened a fractious debate over the probity of lawmakers, whose reputation with the British electorate has suffered from a series of scandals. With a general election on May 7, both parties moved quickly to try to limit the damage.

The episode is particularly problematic for Mr. Rifkind, whose responsibilities give him high visibility and access to highly sensitive information. He stressed that the allegations against him were not related to intelligence or security issues.