"It is a sad day for democracy when the Prime Minister is reduced to poring over media transcripts to determine if one of her Ministers is telling the truth," says National Party Leader John Key.

"David Benson-Pope had no choice but to resign over his evasive answers on his involvement in the sacking of Madeleine Setchell from the Environment Ministry.

"It is regrettable that it took so long for this issue to reach this point."

Mr Key says according to media reports today, Helen Clark has known about Mr Benson-Pope's crucial ‘free and frank' comments since Wednesday.

"So the question needs to be canvassed as to whether the Prime Minister would have acted at all if questions had not been posed by the media and the Opposition."