Who wrote John Key's mystery S&P email?

Prime Minister John Key. Photo / Mark Mitchell

No one is confessing to being the economist who authored an email about Standard & Poor's that has landed Prime Minister John Key in hot water.

BNZ, ANZ, Westpac and ASB Bank economists say it wasn't them.

One economist sent Mr Key an email following a breakfast meeting offering Mr Key a "one-liner" he could use from what was said at the meeting.

The economist, whom Mr Key won't name, described an inference he had taken from what the credit rating agency had said.

The inference the economist took was that a ratings downgrade was more likely if there was a change in Government at the November election.

By the time Mr Key used his one-liner in Parliament, his story was that Standard & Poor's had said New Zealand was more likely to be downgraded if there was a change in Government.

The economist guessed wrong in any event, because New Zealand was downgraded less than a month later by both Standard & Poor's and Fitch.

Standard & Poor's denied saying what Mr Key alleged.

ANZ chief economist Cameron Bagrie was not at the breakfast meeting in Auckland and a spokeswoman said another colleague of his who was there was not the author.

The BNZ's Stephen Toplis said it had not been him nor anyone at the BNZ.

Westpac chief economist Dominick Stephens said he had not sent the email but wouldn't comment when asked if he knew who had.

ASB Bank economist Nick Tuffley said he was at the function but didn't send the email.

Labour has lodged a breach of privilege against Mr Key, accusing him of misleading the House.