The Labour Party is accusing a senior minister of being in contempt of Parliament, saying he misled the House when The Hobbit movie project was under threat of being moved overseas.

Labour MP Trevor Mallard has written to Speaker Lockwood Smith asking him to investigate Economic Development Minister Gerry Brownlee for his answers to questions at the time ministers were negotiating with Warner Bros executives.

Last year, the two movies were subjected to a boycott from several international actors' unions, including the Australian Media, Entertainment and Arts Alliance and its New Zealand affiliate, Actors' Equity.

Warner Bros eventually decided to make the two Hobbit movies in New Zealand, having secured a change to employment laws and up to $34 million in additional tax breaks.

In his letter, Mr Mallard said Mr Brownlee made statements on October 26 to the House which effectively said the boycott was the main cause of the uncertainty over The Hobbit.

But this did not square with an email from Sir Peter Jackson to Mr Brownlee's office a week earlier, which said: "There is no connection between the blacklist (and its eventual retraction), and the choice of production base for The Hobbit. What Warners requires for The Hobbit is the certainty of a stable employment environment."

Parliament's standing orders give examples of contempt, including deliberately trying to mislead the House.

"It is not plausible for Mr Brownlee to argue that he was confused or mistaken when he made these misleading statements," Mr Mallard said.

"We now know that he had received unequivocal advice from Sir Peter Jackson that the reason for Warner Brothers reconsidering the filming location for The Hobbit had nothing to do with the action of the unions.

"The only credible explanation for these statements is that they were designed to deliberately mislead."

He asked Dr Smith to refer the matter to the privileges committee.

Sir Peter has said there is no contradiction between his email and his earlier statements that the boycott was "endangering thousands of New Zealand jobs and hundreds of millions of dollars of foreign income".

He said last month: "This is why Warner Bros lost all confidence in filming in New Zealand - because they had just witnessed how a tiny and capricious union, manipulated by an offshore agency, could bring a multimillion [dollar] production to its knees - for no legitimate reason."

The apparent inconsistency in Sir Peter's positions has been used to push the claim that Warner Bros and Sir Peter used the situation to lean on the Government and extract a law change and extra cash, even though the boycott had been lifted and unions had promised no more industrial action.

Sir Peter and a spokesman for Mr Brownlee have both said the Government did what was necessary to secure the films for New Zealand.