The Big Guns has escalated to a fiery exchange as they debate Mark Latham backing One Nation and calling Opposition leader Bill Shorten a liar.

The conservative commentator and former Labor leader has teamed up with Pauline Hanson’s One Nation to boost the party’s chances in the upcoming by-election.

He’s recorded a robocall, calling Bill Shorten a liar and urging voters in the Queensland seat of Longman to support minor parties.

“I’m Mark Latham, former Labor party leader. I’ve had personal experience with Bill Shorten’s dishonesty. He just lies and lies and lies.

“The reason we’re having a Longman by-election is because Shorten lied about the citizenship of this Labor MPs.

“Whatever you do, don’t reward Shorten’s dishonesty.”

One half of the Big Guns, former Labor politician Graham Richardson, has ripped into Latham for turning on his former party.

“When the Labor party makes you what you are, when you become leader of that party, after a membership of 20 or 30 years… to turn on them the way he has I find really, really sad.”

Andrew Bolt isn’t having it, questioning why Latham shouldn’t have the freedom to call it “as he sees it”.

“If he does think he’s a liar and bad for the country does Graham really expect a man to shut up just because someone in Labor once did him a favour?”

Richo has fired up and defended Labor, admitting he may be critical of the party’s leaders but would never think they’re the “wrong choice” for the country.

Hear the fiery exchange in full