The Justice Secretary has said that there is "anger and incredulity" among Labour MPs over allegations that a number of ex-cabinet ministers were prepared to lobby ministers for cash.
Stephen Byers, Patricia Hewitt and Geoff Hoon, who were secretly filmed as part of an investigation by the Sunday Times and Channel 4's Dispatches programme, have been suspended from the Parliamentary Labour Party pending an investigation into the claims.
All three deny any wrongdoing and Mr Byers has referred himself for a parliamentary standards inquiry.
Mr Straw told Today presenter John Humphrys that their behaviour "prima facie, does indeed bring the Parliamentary Labour Party, as well as Parliament, into disrepute, because it appears that former cabinet ministers are more interested in making money than in properly representing their constituents.
"And that's why there is such anger in the parliamentary party, as well as - I may say - incredulity about their stupidity in allowing themselves to be suckered in a sting like this."
And he added that an inquiry had shown "there is not a single scintilla of evidence of any impropriety whatsoever" by current cabinet ministers.