Labor MP Melissa Parke has lashed out at her party for supporting the Federal Government's "utterly repugnant" offshore processing regime following a High Court ruling upholding the policy of detaining asylum seekers on Nauru.

Key points: High Court brings down majority ruling finding immigration laws constitutional

High Court brings down majority ruling finding immigration laws constitutional Retiring Labor MP Melissa Parke says laws are in "serious violation of our international legal obligations"

Retiring Labor MP Melissa Parke says laws are in "serious violation of our international legal obligations" Labor, Government reaffirm support for offshore detention

The retiring Member for Fremantle said a Bangladeshi asylum seeker's challenge to offshore processing on Nauru would have been successful if the Government had not rushed through amendments to the Migration Act in June last year.

The Government changed the law to close a loophole in the funding arrangements, which it feared could be undermined by the challenge.

The former lawyer at the United Nations took a swipe at the Opposition for supporting the hurried legislation and said Australia's laws were "certainly a serious violation of our international legal obligations and are utterly repugnant in a moral sense".

"It was the Government's despicable and rushed amendments to the Migration Act in June last year, which were unfortunately supported by the Opposition, that resulted in today's High Court win," she said in a statement to Lateline.

"The High Court made it clear that the applicant would have been successful in arguing that the Commonwealth and the Minister acted beyond their power in detaining her on Nauru, if not for the 2015 amendments which had retrospective effect."

Dutton: 'We aren't going to put people in harm's way'

Ahead of the ruling, Immigration Minister Peter Dutton signalled his intention to send a group of 160 adults, 37 babies and 55 children currently in Australia back to Nauru.

"Once the medical assistance has been provided to that person and it's no longer required, then people are then returned to Nauru," Mr Dutton said.

"So there will be medical advice that's provided, and we'll look at the individual cases, but I've given an assurance — I'm not going to send children back into harm's way."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 9 minutes 41 seconds 9 m Peter Dutton speaks to 7.30 about the High Court case

During the High Court case the Government changed the law to close a loophole in the funding arrangements, which it feared could be undermined by the challenge.

The Government's current arrangements were found to be constitutional by a majority of the High Court's bench.

However the most recent appointment to the bench, Justice Michelle Gordon, issued the lone dissenting judgement that the laws rushed through in June were invalid.

Ms Parke said she raised concern over the numerous inquiries and reports on abuse of asylum seekers during debate over the legislation.

She said she had "expressed concern that the extremely broad wording of the bill and its retrospectivity would appear to validate the detention of asylum seekers and all actions and arrangements in offshore detention centres since August 2012".

"This has come to pass and the result will be vulnerable families, including children, potentially being sent back to an extremely unsafe environment, and impunity for perpetrators of abuse," she said.

After Wednesday's decision, shadow attorney-general Mark Dreyfus said the policy of offshore detention should not necessarily be abolished altogether.

"I don't think it's necessary to say ... that it's time to end that policy," he said.

Government urged not to return people to Nauru

One of the asylum seekers, who was held in detention on Nauru before giving birth to a son in Darwin last year after complications during the pregnancy, has told 7.30 she fears for her child if they are sent to the island.

"It's like dying. It's waiting for dying," the mother said.

Paediatrician Dr Josh Francis, who treats children in detention in Darwin, also told 7.30 the disruption of immigration detention could have lasting negative effects on children.

Australian Human Rights Commission president Gillian Triggs said under Australia's international obligations, the best interests of the children expected to be sent back to Nauru should still be the primary consideration.

"[The] High Court decision in no way requires the Government to return the children and their families to Nauru," she said.

"Given the risk of harm to these children and their need for ongoing medical care, we strongly urge the Government not to return them to Nauru."

Mr Turnbull told Parliament the Government would consider the judgement but that current policy had kept Australia's border secure and prevented drownings at sea.

"The people smugglers will not prevail over our sovereignty," he said.

"Our borders are secure. The line has to be drawn somewhere and it is drawn at our border."

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