"It's what I was saying all along. This is the sort of proof we have been looking for," Ms Kelly told Radio New Zealand, which obtained the email under the Official Information Act (OIA).
The email showed Warner Bros. wanted "stability" to film the movies in New Zealand and was worried about "grey areas" of employment law.
The Government secured the movies in October by an urgent amendment to the law which prevented independent contractors from claiming entitlements as employees, as well as an agreement to increase the tax concession for big screen productions.
The report said the email was signed "Peter J" -- apparently director Sir Peter Jackson -- and was sent to the office of Economic Development Minister Gerry Brownlee who was involved in the negotiations with Warner Bros.
It said there was no connection between Actors' Equity union action against The Hobbit movies and choice of location, which contradicted government statements at the time -- which were that Warner Bros. was concerned about strife caused by the blacklisting of the movies because of a row over collective pay conditions.
Union opposition was withdrawn after an outcry from New Zealanders who would lose their jobs if the movies were not made here.
Ms Kelly said she had always maintained that the union action had nothing to do with the debate, which was about employment law, the high New Zealand dollar and subsidies.
"What we were saying was these actors simply wanted to negotiate."
Warner Bros. raised concerns about a successful 2005 court case where former Weta Workshop model maker James Bryson was deemed to be an employee, not a contractor.
"They were looking to use the dispute to ratchet up both money and employment law reductions for workers in the industry."
Ms Kelly said the Government had refused to release a Crown Law opinion about the legality of seeking a collective contract for Hobbit workers.
"We think that's because it doesn't say what they claimed it said."
She said the OIA documents included letters from people in the film industry asking the Government not to change the subsidy regime, that it would be destabilising.
"A whole lot of advice that they chose to ignore."
