A United Nations body has taken the “extraordinary” step of calling on Australia to review its domestic laws in a ruling that it had breached multiple international human rights laws.

The ruling coincides with the Australian government being taken to the UN over alleged breaches of international law by indefinitely separating more than 60 members of 14 refugee families on Nauru.

The working group on arbitrary detention, established by the UN Commission on Human Rights in 1991 to report to the Human Rights Council, had examined the case of Edris Cheragi, an Iranian man and Christian convert who sought asylum in Australia.

Cheragi has been detained in various detention centres and in the community since 2012, but in 2015 was charged with criminal offences and had his bridging visa cancelled. He has never been convicted.

Instead Cheragi was placed in “administrative detention” under the laws of the Migration Act, and has been in detention ever since.

The working group said Cheragi’s circumstances were just the latest of many cases of arbitrary detention in Australia, and ruled the Australian government had breached multiple articles of the universal declaration of human rights and the international covenant on civil and political rights.

Cheragi’s detention was based “purely on his earlier exercise of the legitimate right to seek asylum and is therefore arbitrary”.

“The [Australian] government has not provided any explanation for the continued detention of Mr Cheragi since 30 October 2015 aside from the fact his visa was cancelled on 11 September 2015,” it said.

It acknowledged that Cheragi’s detention was in accordance with the domestic act, but said Australia must ensure detention was also consistent with international law.

It called for the government to review its Migration Act, immediately release Cheragi and give him access to compensation and other reparations, as well as launch an independent investigation into his detention and ensure action against those responsible for the violation of his rights.

It was the seventh working group opinion in two years calling for the release of individual asylum seekers from Australian detention centres.

The Australian government told the working group it was committed to “an effective and robust international protection program”, and that it considered mandatory immigration detention to be an essential component of strong border control.

Cheragi had been granted a bridging visa and released from detention, the government said, and was only redetained after being arrested and charged.

Alison Battisson, the director principal of law firm Human Rights for All and the source of Cheragi’s submission to the working group, described the call for a review of the act as “an extraordinary step” towards a sovereign nation.

“In doing so the UN has highlighted Australia’s appalling practice of using detention as a default mechanism for asylum seekers and refugees,” she said. “How many more times will the Australian government – now led by the ‘new’ Liberal party – ignore the recommendations of a sub-body of the very council it campaigned to get a seat on?”

Cheragi has a history of mental illness and continues to be assessed as being at high risk of self-harm. Cheragi’s asylum claim has been assessed and denied, the government told the working group.

The case is one of two significant interventions involving the UN in Australia’s increasingly condemned immigration detention system.

A family separation case, brought by the Human Rights Law Centre, is seeking orders from the UN’s Human Rights Committee, the world’s highest human rights authority, for the immediate reunion of the families.

“Instead of forcing people to choose between the cruelty of indefinite detention and the cruelty of family separation, the government should just put a handful of people on a plane and reunite these families in Australia,” said Daniel Webb, the director of legal advocacy for the Human Rights Law Centre.

Among the families are five babies born in Australia whose fathers remain on Nauru.

Some families were separated because they arrived on different dates either side of the federal government’s 2013 pronouncement that all boat arrivals would be sent offshore.

Others were split when one member was taken to Australia for urgent medical treatment and forced to leave members of their family behind.

Nasreen and her adult daughter Mahboubeh are currently in Australia for Nasreen to receive medical treatment. They have not seen Nasreen’s two older children – Narges and Daryoush, who were made to stay on Nauru – for more than four years.

“When I transferred to Australia for treatment it was as if someone suggested that I choose between my left and right hand,” Nasreen said. “Whoever separates a mother from her children does not help, but tortures them. All of my medical records show my physical and mental illnesses have not improved after moving to Australia. No mother can be well when her son and daughter suffer mentally and physically.”

The Afghan Hazara family have all been found to be refugees in need of protection, including their father, who arrived in Australia earlier and has settled here. He is not allowed to live with his wife and daughter in Sydney.