Leader of the House Gerry Brownlee was delegated to answer questions from New Zealand First MP Denis O'Rourke on Mr Key's behalf but said there was no ministerial responsibility.
He claimed immunity on the grounds that the matter related to John Key as National Party leader, not his role as Prime Minister, and questions in Parliament can be directed only at members of the executive on their responsibilities as such, not as political leaders or Members of Parliament.
Labour's Trevor Mallard questioned how that was the case when Mr Key's response to the police dropping the case had been made by Mr Key as Prime Minister - he issued a press statement on Prime Ministerial letterhead.
Mr Brownlee said that as evidence that Mr Key had been acting as National Party leader, he had got his own private lawyer to act on the matter, not Crown Law.
Labour also pointed to a conversation between Barack Obama and Dmitry Medvedev at the conference in Seoul having been picked up by microphones and widely broadcast.
David Parker: "What was it about John Key's and John Bank's conversation in Epsom that made it more sensitive than a conversation between the Presidents of the United States and Russia?"
Mr O'Rourke, referring to the part of tape in which Mr Key reportedly says that New Zealand First's supporters were dying off, asked "has the Prime Minister sought or received any information on how many elderly New Zealand First supporters died during the course of the police investigation?"