The former Labor MP, Craig Thomson, has labelled his old party hypocritical and will vote against its legislation to excise the Australian mainland from the nation's migration zone.
The controversial bill was introduced into Parliament on Wednesday and is set to pass the lower house before the end of this month with the support of the Coalition.
However, Mr Thomson, for the second time in two days, will vote against Labor on legislation, saying the party's about-face from its position on the bill six years ago was too much to stomach.
"One of the main reasons I decided to enter Parliament was because I was appalled at the way Australia was treating asylum seekers,'' he said. ''But now we are seeing a Labor government going back to the Howard years by excising mainland Australia from the offshore processing centres in an appeal to the worst elements of human nature.
"The Labor Party was right in 2006 to oppose this and the reasons then apply just as much now."
Mr Thomson told the ABC this morning: "It's an absurd proposal that Australia isn't part of Australia.
"We need to be concentrating on the regional approach, rather than pandering to particular redneck views in our communities."
On Tuesday night, Mr Thomson voted to amend a bill to free Australian research from unintended consequences of a defence treaty with the US.
Mr Thomson represents the seat of Dobell on the central coast. He was suspended from the ALP in April pending civil and criminal investigations into his use of a union credit card before entering Parliament.
Should he be cleared following a criminal investigation, it is understood he has not ruled out running as an independent.
In 2006, the Howard government tried to excise the mainland from the migration zone but failed amid fierce internal resistance from moderates. Now, Labor wants to introduce the measure as part of its policies to try to stop the escalating flow of boats.
Under the change, anyone who arrives on the Australian mainland by boat will be sent offshore for processing to Nauru or Manus Island and would no longer be entitled to be processed onshore or receive a bridging visa and limited work rights.
Mr Thomson's resistance will not stop the passage of the bill because the Coalition is expected to support it.
In 2006, the Immigration Minister, Chris Bowen — then in opposition — slammed the measure as a stain on the national character.
Addressing Parliament in August 2006, Mr Bowen said the proposal to excise Australia was "a bad bill with no redeeming features. It is a hypocritical and illogical bill. If it is passed today, it will be a stain on our national character".
However, he said yesterday he had changed his view because the measure was part of a package to try and stop people getting on boats.
''If I have a choice between saving somebody's life and being entirely consistent with something I said in 2006, well, I'll go for saving the life, thanks very much,'' Mr Bowen said.