Labor Leader Bill Shorten has labelled Clive Palmer Australia's "number one digital serial pest".
Mr Palmer is in the midst of attempting a political comeback, with his campaign sending out unsolicited text messages and releasing a politically-themed mobile game.
"I'm going to take Clive Palmer seriously when he pays the $70 million he owes the workers and his creditors," Mr Shorten told reporters in Brisbane on Thursday.
"I'll take Clive Palmer seriously when he pays back the taxpayers of Australia who have stepped in to his shoes to fulfil his obligations as a conscientious employer."
Mr Palmer's company Queensland Nickel folded with debts of $300 million in 2016, causing the loss of hundreds of jobs at its Townsville refinery.
"He should just pay the workers, do his proper obligations, and then he can have a welcome to hear whatever he has to say on anything else," Mr Shorten said.
Meanwhile, Mr Palmer is back among the nation's 50 richest people, with Forbes estimating his fortune at $US1.8 billion ($A2.5 billion).
This places him at number 20 thanks to court-ordered royalty payments from CITIC Pacific Mining's Sino Iron project in Western Australia.
