The Ombudsman has ordered the NZ government to release documents about the deal it struck to ensure the Hobbit movies were made in New Zealand.

Radio New Zealand applied for the documents in November 2010 under the Official Information Act but ministers refused on the grounds they were commercially sensitive.

The broadcaster appealed the decision and on Thursday Ombudsman David McGee ruled 18 documents, including emails between Hobbit director Sir Peter Jackson and government officials, must be released.

The government secured the three movies by changing employment laws and beefing up the tax rebate sweetener for the productions.

Unions fought the law changes and the Labour Party accused the government of chequebook legislation.

In his 29-page ruling Mr McGee says the information in the documents doesn't pose serious commercial risks.

Ministers must hand over the documents on or before March 1 unless the cabinet overrules Mr McGee by invoking a veto which was introduced in 1987 but has never been used.

The first of the Hobbit trilogy, An Unexpected Journey, premiered in Wellington in November and has been a huge success internationally.

NZ Prime Minister John Key says production generated 3000 extra jobs and New Zealand gained priceless tourism publicity.