Two former senior British government ministers have denied wrongdoing after being caught in a hidden-camera sting appearing to offer access to politicians and diplomats in return for cash.

Jack Straw, who was foreign secretary under Labour Party Prime Minister Tony Blair, and Conservative former Foreign Secretary Malcolm Rifkind, were secretly filmed by reporters posing as representatives of a Hong Kong-based communications agency.

Rifkind was recorded saying he could arrange "useful access" to ambassadors, while Straw spoke of using "charm and menace" to change politicians' minds.

The sting has reopened debate about political lobbying.

Rifkind and Straw, who are still lawmakers, have referred themselves to parliament's standards watchdog.

Rifkind said Monday that allegations of wrongdoing were "unfounded." Straw said his conversation related to activities he might undertake once he left Parliament.