Deputy Premier John Barilaro is facing accusations he has broken the Ministerial Code of Conduct by not declaring a donation to cabinet while debating a bill which would overturn a decision to cull thousands of wild brumbies in the Snowy River.

Peter Cochran is a former Nationals Member for Monaro and owner of Cochran Horse Treks.

He has been fiercely lobbying against a brumby cull announced by the NSW Government in 2016.

NSW Deputy Premier John Barilaro is accused of breaking the Ministerial Code of Conduct over the receipt of funds. Picture: AAP (AAP)

Mr Cochran and his wife donated $5000 each to the National Party ahead of Mr Barilaro’s successful 2011 campaign for the seat of Monaro.

The declarations show Mr Barilaro as the recipient of the money.

Mr Barilaro told 9NEWS he has been fighting to save the Snowy River brumbies for almost a decade and Mr Cochran’s donation did not influence the decision to stop the cull.

Mr Cochran‘s company charges riders up to $2040 for a five-day trek through the Kosciuszko National Park.

One of the selling points outlined on their website is to see “brumbies in the wild.”

Barilaro received money from a former National MP, Peter Cochran, now running a horse trekking company. (Supplied)

Mr Cochran's company charges $2000 for a five-day trip through the Kosciuszko National Park. Picture: AAP (AAP)

Mr Cochran also claimed on Facebook he had helped draft the bill that would overturn the proposed cull.

“The Bill was originally drafted under instruction from myself by pro-bono solicitor Richard Smallwood," Mr Cochran said.

A bill to stop the cull in favour of a “horse management plan” was introduced to NSW Parliament by Mr Barilaro last week.

9NEWS has been told by multiple sources that during a cabinet debate about the bill, the Deputy Premier did not declare the donations from Mr Cochrane, any influence he may have had on the bill, or any conflict of interest.

The Ministerial Code of Conduct states a minister must declare an interest to cabinet.

“The nature and extent of the interest is such that it could objectively have the potential to influence a Minister in relation to the decision or action,” the code states.

Mr Barilaro insists there is nothing to declare.

“There is no conflict of interest in this case, this is a public issue and one that I've campaigned on," Mr Barilaro said.

“I have complied with the code of conduct.”

A brumby grazes on grass outside Canberra in a 2016 protest. Peter Cochran has been lobbying against a brumby cull. Picture: AAP (aap)

Premier Gladys Berejiklian is responsible for enforcing the Ministerial Code of Conduct.

“The Deputy Premier has advised me that he considers he has acted in accordance to the Ministerial Code of Conduct at all times,” Ms Berejiklian said.

Mr Barilaro confirmed Mr Cochran did submit some notes to be considered in the bill, but what was presented to parliament was prepared by Parliamentary Counsel.

“This looks like an open and shut case, a clear breach of the Ministerial Code of Conduct,” Opposition Leader Luke Foley said.

Mr Cochran told 9NEWS he has been campaigning against culling brumbies for years, and his business interests have never played a part in any of it.

The original brumby cull was announced in 2016 and proposed to reduce the numbers from 6000 to 3000 over a decade.