Senator Jim Molan has withdrawn from a scheduled appearance on the ABC's Q&A program, saying he can no longer defend the Liberals after being placed in an unwinnable position on its New South Wales Senate ticket.

The former Army major general was bumped down the ticket to third spot at a meeting of Liberals on Saturday, behind regional powerbroker Hollie Hughes and former acting Liberal Party director Andrew Bragg.

The Liberals and the Nationals in New South Wales run a joint Senate ticket, and the Nationals hold the third spot on the ballot, meaning Senator Molan has been relegated to the generally unwinnable fourth position.

In a text to the ABC on Saturday evening, Senator Molan voiced his concern.

"I may not come on the show on Monday," he said.

"Just to make you aware. I cannot bring myself to defend my party at the moment.

"I will confirm tomorrow."

This morning, Senator Molan pulled out, saying again he, "would find it hard to defend my party".

He later tweeted to clarify he was talking about the preselection process rather than the Liberal Party's policies.

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Senator Molan's surprise demotion follows a short career in Federal Parliament.

He was sworn in as a senator for New South Wales in February this year, in the wake of the dual-citizenship fiasco which cut a swathe through Canberra.

The seat he took up originally belonged to former deputy Nationals leader Fiona Nash, who was disqualified by the High Court for being a British citizen by descent.

Ms Hughes was in line to replace Ms Nash, until the nation's highest legal authority ruled she too was disqualified because she took up a taxpayer-funded job in the wake of the 2016 election.

That was despite Ms Hughes resigning that position the moment Ms Nash was kicked out of Parliament.

Mr Bragg had been in the running to become the Liberal candidate for the Wentworth by-election, caused by the resignation of former prime minister Malcolm Turnbull.

But he pulled out of that contest after being promised a winnable spot on the party's Senate ticket.