The union was sent a copy of a letter from Peters to Messara which outlines what is required for the review.
In the letter, Peters specifically asks Messara to focus his review on the thoroughbred industry.
"This letter is to formally seek your interest in undertaking a high-level assessment on my behalf of the racing industry in New Zealand, with a focus on how the current model supports the financial viability of the thoroughbred racing sector.
"Your review should analyse the current situation, with particular emphasis on the thoroughbred racing code."
Messara's review of the industry was previously thought to be an investigation of the whole racing sector that did not have a specific focus on thoroughbreds.
Peters said Messara's review "will also assist the Government in determining if the current Racing Act 2003 and the proposed Racing Amendment Bill are fit for purpose".
The thoroughbred racing focus of Messara's review could leave the harness racing and greyhound codes out in the cold if Messara recommends changes to racing legislation to benefit the galloping code.
The revelation Peters wants the future prosperity of thoroughbred racing specifically examined comes as his close ties to the code are in the spotlight. Last month, the Herald
reported that in September thoroughbred heavyweights Sir Patrick Hogan and wife Justine Lady Hogan took out a full-page advertisement in The Informant urging the racing industry to support NZ First because of its racing policies.
The Electoral Commission said it was looking into the advertisement which was not declared in New Zealand First's election expenses return.
In North & South magazine late last year, Hogan said he had helped NZ First leader Peters develop his racing policy.