New South Wales MP Andrew Gee has resigned from the Nationals due to the party's decision to oppose the Indigenous Voice to Parliament.

Mr Gee, who represents the NSW seat of Calare, will move to the crossbench effective immediately, rejecting the Nationals' position on a constitutionally enshrined Voice.

On Friday he said the National Party's recent decision to oppose the Voice, a position he 'fundamentally disagrees' with, gave him no choice but to resign.

"The recent decision by the National Party to oppose the Indigenous Voice to Parliament, and also witnessing the devastation our region has experienced over the past few weeks, has really brought home to me the importance of being able to stand up and be counted," Mr Gee said.

"I can't reconcile the fact that every Australian will get a free vote on the vitally important issue of the Voice, yet National Party MPs are expected to fall into line behind a party position that I fundamentally disagree with, and vote accordingly in Parliament.

"While I respect the views of my colleagues, this just isn't right."

Mr Gee's decision to resign from the Nationals comes after the party formally opposed the Voice to Parliament late last month.

After the party announced their position, Mr Gee said he didn't feel able to speak freely about his personal beliefs on the Voice to Parliament.

He also doesn't see the Nationals changing their position on the Voice.

"However, in the days after stating my own position of support for the Voice, I felt that I didn't have the unfettered freedom to speak that I needed," Mr Gee said.

"As the discussion on this issue around Australia builds, I want that freedom to put forward my point of view as I don't foresee the Nationals' policy on the Voice changing."

A referendum on the Voice to Parliament is expected in the second half of 2023.