An Australian couple who abandoned a baby boy born via a surrogacy arrangement in India misled High Commission staff in New Delhi and were repeatedly warned the baby could be left stateless, documents show.

Freedom of Information (FOI) documents obtained by the ABC's Foreign Correspondent program reveal startling new information about the case, which saw the couple return to Australia with a baby girl while leaving her healthy twin brother behind, with the full knowledge of Australian Government officials.

The documents show Department of Foreign Affairs and Trade (DFAT) staff, as well as the Australian High Commission in India, knew the couple was from New South Wales, where it is illegal to engage in international surrogacy arrangements.

The highly redacted FOI documents shed more light on the Australian couple's desperate bid to leave behind the twin boy.

Emails and cables between the Australian High Commission in New Delhi and Government officials in Canberra reveal the couple travelled to India late in 2012 to seek citizenship for a baby girl but told consular staff they would be leaving her twin brother behind because they could not afford him, they already had a son at home and wanted to "complete their family" with a girl.

According to the documents, the Australian man then misled consular staff when he told them he would be giving the boy to some friends in India "who were unable to conceive a child".

A cable from Australian High Commission staff to Canberra in early 2013 said: "The proposed adoptive parents are in fact not close family friends of the biological parents, but are known to the biological parents through a mutual friend."

The couple was repeatedly told abandoning the boy could leave him stateless because India did not recognise surrogate children as citizens.

"If the parents do not apply for Australian citizenship for the child, the child will be stateless in India ...our ability to provide assistance to a non Australian citizen is limited," a DFAT email on December 19, 2012 said.

The FOI material shows the High Commission in New Delhi sought "urgent" advice from three separate government departments in Canberra, and also raised the issue with the office of then prime minister Julia Gillard.

But three days later, consular staff were seemingly given the green light to allow the Australians to return home with just the baby girl.

Concerns for abandoned baby boy

Advice sent from DFAT in Canberra to the High Commission in India stated: "While we are concerned at the potential impact of the welfare of the child, this is a matter that needs to be addressed by Indian authorities."

High Commission staff were then urged to monitor the situation closely.

The documents indicate the abandoned boy is entitled to Australian citizenship, but it is not automatically granted it without it being applied for.

By January 14, 2013, a further cable revealed the High Commission's concern with its own decision making.

An Immigration document would suggest at that time no papers had been seen as officials were still concerned about the risk of the child becoming stateless.

In December 2012 we became aware of the a case involving twins born through surrogacy arrangements in India. We were informed by the parents of the children that they did not wish to take parental responsibility for both children and they intended to transfer responsibility for their male child to a couple of Indian citizenship. The approach prescribed for cases such as this was to simply discuss them in broad terms with like-minded missions and the Indian authorities. However the risks involved include that the child becomes stateless and their welfare is compromised. We are therefore concerned that our approach would leave us exposed to media and parliamentary scrutiny. We are however continuing to monitor this situation closely to ensure that the male child is not left stateless and his welfare is maintained.

DFAT said the boy was formally adopted in India, although no documentation supporting that has been made public.

A DFAT memo of August 10, 2014 notes: "I believe they did manage to get a copy of the local adoption order for the child left in India".

Another internal DFAT document of September 9, 2014 states: "I am sure DIBP (Department of Immigration and Border Protection) would have extensive records on this (in reality, DFAT didn't get overly involved as the child was never considered an Australian citizen, and thus was never issued a passport)".

"I believe DIBP did manage to get a copy of the adoption order," the DFAT note said.

However, the FOI documents obtained by the ABC from Foreign Affairs and Immigration do not show any evidence the adoption papers have ever been seen by the Australian Government.

Legal advice provided to the Australian High Commission in India dated January 15, 2013 notes that "presuming that the parents of the adopted male child fail to provide adequate evidence satisfying the provisions of the Hindu Adoption Act, the male child shall, in that case, be deemed to be the natural child of Australian Citizens".

Staff said baby may have been sold

When the ABC first revealed the case in October last year, the Chief Justice of the Family Court, Diana Bryant, said she had been told by concerned consular staff the baby may have been sold.

"They expressed to me that in fact money had changed hands, and if that's true, then that's basically trafficking children," she said.

"We're commoditising children and that's a huge concern. It's in breach of all sorts of human rights conventions – it's a criminal offence in many places."

The documents do not reveal whether a financial transaction took place.

If money was paid, any adoption would be deemed invalid under India's Hindu Adoption Act.

The FOI documents also contain correspondence from a Supreme Court advocate in India, who advises the Australia High Commission to "ensure that the adoption has been made in compliance of the conditions contained in sections 5 to 11 of the Hindu Adoption Act".

The FOI material shows Australia has a limited jurisdiction to check on the welfare of the abandoned boy.

The documents also briefly mention a second concerning surrogacy case.

The ABC understands in that instance, twins born via surrogacy were left in India after the Australian parents' marriage broke down.

DFAT has confirmed both of these children are now in Australia.

The Indian case echoes the recent case of baby Gammy, who was born in Thailand to a surrogate mother and whose Australian parents only brought back his twin sister.