Mr Stoner, who was leader of the NSW Nationals until he quit in October, has launched defamation proceedings in the NSW Supreme Court claiming his reputation was damaged by five broadcasts in June and August last year.

It is understood the legal action was launched after Jones and Mr Buckingham did not accede to demands they each pay Mr Stoner a six-figure sum.

In four broadcasts on radio 2GB in June, Jones attacked Mr Stoner as "dumb as a plank of wood" and accused him of describing a group of anti-coal seam gas protesters at Bentley on the NSW north coast, as "professional bludgers".

Jones also labelled Mr Stoner a "gutless wonder" and an "intellectual incompetent".

On August 29, Jones interviewed Mr Buckingham in relation to the Shenhua coal mine in the Liverpool Plains.

Mr Buckingham said "the first thing Andrew Stoner did ... when he came into government was to facilitate one of the biggest coal mines in the heart of the Liverpool Plains, Shenhua".

He accused Mr Stoner of "undermining his constituency, the farmers".

They also discussed evidence before the Independent Commission Against Corruption about the former mining mogul Nathan Tinkler.

ICAC heard allegations that in 2010 and 2011 then NSW Labor government ministers Eric Roozendaal and Joe Tripodi had taken steps to help Mr Tinkler secure approval for a coal loader in the Newcastle suburb of Mayfield.

"Lots of money flowed from Nathan Tinkler and his interests to the National Party and after they got into government Andrew Stoner and [another Nationals MP] did the bidding of Nathan Tinkler," Mr Buckingham said.

"They kept in train the process that Joe Tripodi and Eric Roozendaal set in place."

In his statement of claim Mr Stoner says the broadcasts conveyed Mr Stoner was not fit to be NSW Nationals leader or Deputy Premier and that he favoured miners over the welfare of the community.

It says Mr Buckingham had imputed that Mr Stoner "acted corruptly in promoting the coal interests of Nathan Tinkler as a payoff for donations to the [National] party". Mr Stoner says the imputations are false.

However Mr Buckingham told Fairfax Media the legal action was "designed to try to intimidate the Greens and others from criticising the National Party's failure to stop coal mining on the best farming country in Australia" just weeks out from an election.

Mr Stoner, who is not recontesting his seat of Oxley at the March 28 election, said the legal action "is being pursued by me through my lawyers as a private citizen, not as a member of the government, which I will cease to be prior to any court hearing".

Jones did not respond to an invitation to comment.