Andrew Little's joining with the Greens in condemning the Prime Minister over allegations John Key's levelled at Green MP Mojo Mathers.

Key's accused Ms Mathers of being involved in a foreign trust, an accusation she rejects.

She said she's the beneficiary of a UK-based family trust.

Little said it was totally tasteless and out of order, and if he was a man, Key would stand and apologise.

"She should never have been put in that position. She's the only deaf member in the house and this is New Zealand Sign Language Week. It was just totally tasteless."

Green Party Co-leader James Shaw is critical of Key's actions.

"It was a personal attack designed to deflect attention from the fact the Government isn't really doing anything to close down the use of New Zealand as a tax haven here."