Federal Member for Bendigo Lisa Chesters was among of a minority of Labor MPs who voted on a motion to close Australia's offshore processing centres in Nauru and Papua New Guinea in Parliament on Tuesday.
The motion did not have enough votes to pass but it highlights division within the Opposition over asylum seeker policy.
The move came after Labor immigration spokesman Richard Marles' repeated comments that he fully supports offshore processing.
Just three weeks ago Mr Marles told the National Press Club that the Rudd government should never have dismantled the offshore centres.
Ms Chesters said her decision to be one of the minority of Labor MPs in support of the motion should not be a surprise.
"When I was preselected as candidate for the Labor party I was really honest that I would always advocate for an onshore regional processing solution," Ms Chesters said.
"I was very open and honest with the Bendigo electorate when I was a candidate.
"In many ways today was just me being true to my word."
Ms Chesters said for asylum seeker processing to be brought back to the Australian mainland, the United Nations would have to be involved.
"During the Fraser government, the UN, with support of Australia and Vietnam, established a processing centre in Vietnam so those seeking asylum could go direct to a processing centre there," she said.
"I strongly believe that what we need is a regional solution that is carried by the UN."
She said Australia could not address the asylum seeker issue alone but needed to work in partnership with other countries in the region.
She said the government was being secretive and using war-like rhetoric.
"They hold up this pretence that we are about to be invaded and it's simply not true," she said.
"The government is hiding behind the armed forces and the PNG government."