Scotland's First Minister Alex Salmond has been accused in the Lords of "lying to Parliament and other transgressions".
Labour former Scottish minister Lord Foulkes of Cumnock drew gasps of surprise from peers when he levelled the charge at question time.
But when pressed over what the "transgressions" might be, he said only: "I'll tell you later."
His intervention came during a question on the application of the ministerial code at Westminster.
Lord Foulkes said: "The ministerial code in Scotland is so narrow and so lax that the First Minister gets away regularly with lying to Parliament and other transgressions..."
As peers pressed him on what these might be, he said, to laughter from all sides: "I'll tell you later," but added: "Seriously, do we have any reserve powers to look at the ministerial code in Scotland and tighten it up?"
Cabinet Office spokesman Lord Wallace of Saltaire said he was not "sighted" on this particular question.
He added: "But I look forward to the enjoyable evening in which you tell me about some of the transgressions that you feel have happened in the Scottish Executive."
