Australian immigration policy - Controversy continues

Three Liberal backbenchers have defied the prime minister and vowed to cross the floor of parliament to vote against the government's new hardline immigration policy.

Petro Georgiou, Russell Broadbent and Judi Moylan banded together in the lower house as debate on the laws - designed to send all asylum seekers arriving in Australia by boat offshore for processing - began in parliament.

They had harsh words for their own government.

All said they were willing to suffer the political consequences of challenging the majority view of their party, just one day after Prime Minister John Howard called for unity.

"If I am to die politically because of my stance on this bill, it is better to die on my feet than to live on my knees," Mr Broadbent told parliament during an impassioned speech.

"Some warn that any dissent is a form of political death.

"(But) it is not the office of the federal member that is important; it is what you do when in office."

Ms Moylan, whose preselection for her West Australian seat of Pearce is reportedly under threat as a direct result of her outspoken views, particularly on asylum seekers, was equally firm in her resolve.

The parliament could not consign people to detention that was out of sight and out of mind, she said.

"I cannot believe that the citizens of this sovereign country would ever cease to wonder, nor would they ever forgive, were we in this house to acquiesce in silence to pressure from a neighbour on a matter so much at the heart of our principles of justice," she said.

"I for one cannot remain silent."

Mr Georgiou also launched a spirited attack on the policy, describing the bill as the "most profoundly disturbing piece of legislation" he had encountered in more than a decade in parliament.

The dissenters do not have the numbers in the House of Representatives to prevent the Migration Amendment (Designated Unauthorised Arrivals) Bill passing.

But they hope at least one coalition senator or Family First will join Liberal senator Judith Troeth in opposing the laws in the Senate.

The backbenchers' main problems with the policy, announced in April following Indonesian anger over Australia's decision to grant asylum to 42 asylum seekers from the contested Papua province, centre around the detention of children.

They say the changes overturn a hard-won promise by Mr Howard last year to keep children out of detention by placing them in community-based homes.

But they also say asylum seekers will be blocked from access to Australia's legal appeals processes if they are held offshore, and argue that their detention could be indefinite.

Mr Howard tried to brush off the internal rebellion and said the majority view would prevail.

"A lot of changes have been made to accommodate the concerns of some colleagues but in the end, as happens in any democratic party, the overwhelming majority view must be respected.

"That is why we are going ahead with the legislation," he said.

Opposition immigration spokesman Tony Burke says the bill effectively abolishes the Australian border.

"Australia is better than this bill. This legislation before us today undermines our sovereignty, is offensive to our decency and makes a mockery of this parliament," Mr Burke told parliament.