Mr Barilaro this week ruled out an attempt to switch from state to federal politics via a potential three-cornered race with the Liberals and Labor for retiring MP Mike Kelly's electorate.

However, Sky News reported on Tuesday afternoon that leaked messages from Mr Barilaro to Mr McCormack, who is Deputy Prime Minister and federal leader of the Nationals, claimed a lack of support for seeking preselection.

"Don't hide behind the "members will choose the candidate' rubbish, as you were the only one saying such lines," Sky News reported Mr Barilaro's messages as stating.

"Don't you think my branches would have backed me in?

"To feel threatened by me clearly shows you have failed your team and failed as a leader.

"You will never be acknowledged by me as our leader. You aren't. You never will be."

Mr McCormack has defended the level of support he had given Mr Barilaro's contemplation of a run for Eden-Monaro, pointing to previous public statements about welcoming him entering the race and pledging to help.

Mr Kelly resigned from parliament last week citing ill health, having held the bellwether seat for Labor for three of the four full terms since 2007.

Most byelections in Australia have been lost by incumbent governments but Mr Barilaro previously claimed National Party research showed he could have won.

"The Nats had a chance to create history, to change momentum, and you had a candidate that was prepared to risk everything to make it happen, Sky News reported Mr Barilaro's messages to Mr McCormack as stating.

"What did you risk? Nothing. Hope you are proud of yourself."

Mr McCormack said he respected Mr Barilaro's "personal decision not to contest the Eden-Monaro by-election due to family reasons".

"I have always supported the democratic election processes of the National Party of Australia. I wholeheartedly endorse the right of branches to select their local candidates first and foremost.

"My support of Mr Barilaro has been long standing and I respect his position as Deputy Premier and NSW Nationals' Leader.

"Those suffering from drought, recovering from bushfires and dealing with the COVID-19 pandemic are the people I am focused on.

"I will continue to work with all my Nationals' colleagues, federal and state, as well as all elected representatives, to advance outcomes for regional people."