Senior Labor figures have lashed out at Mark Latham, labelling their former leader as an irrelevant, desperate attention seeker.
Mr Latham, who led federal Labor from 2003 until 2005, has announced he's joined the Liberal Democrats.
He's also hinted at a political comeback in order to save "western civilisation" and defend free speech.
"You don't know how bad it is to lose your freedom of speech until it happens to you," he told Sky News on Monday night.
Mr Latham ridiculed the "outrage industry" and "confected offenderati" which he says have taken over the Labor party, and the lefty "sneering, censorious lynch mobs" which were shutting down debates if they didn't like particular arguments.
Mr Latham said the current Labor leadership had gone "cuckoo" and vowed to continue speaking his mind without "some galah pulling the plug out of the microphone".
Shadow treasurer Chris Bowen was dismissive of Mr Latham's latest pronouncement.
"One of the mysteries of public life is why anyone takes this guy seriously anymore," he told reporters at Parliament House in Canberra on Tuesday.
"He once had something to contribute ... that was a long time ago."
Mr Bowen described Mr Latham a "parody of himself" and a "desperate attention seeker who is suffering relevance deprivation syndrome since he left the Labor party".
NSW Labor on Monday backed a motion to ban Mr Latham for life.
Frontbench colleague Brendan O'Connor didn't wish his former colleague ill, but described him as "irrelevant to the Labor Party".
"If he wants to choose to join another political party after getting everything he has got from the Labor Party including his lifelong superannuation that's his choice," he said.
Labor senator Jenny McAllister won't be shedding any tears at Mr Latham's departure from Labor.
"I was horrified by how he pursued (anti-domestic violence campaigner) Rosie Batty."
Liberal Democrats senator David Leyonhjelm said Mr Latham would be just one of 7000 members of the party.
In an interview with Mr Latham on Senator Leyonhjelm's Facebook page, the senator compared returning to politics to getting married a second time.
"It was a triumph of hope over experience," the senator said.
"I thought that would be a bit of a negative to him. But he said, well he'd already been married a second time and he's much better at it the second time. So perhaps he thinks the same about a political career."
Senator Leyonhjelm acknowledged Mr Latham comes with some baggage.
"We've got a fair bit in common, but I've never broken a taxi driver's arm that's for sure. I don't get into blues if I can avoid it," he said.
Senator Leyonhjelm insisted Mr Latham's controversial views on women had suffered a degree of "misinterpretation".
