Assistant Immigration Minister Alex Hawke has declined to intervene in the case of the Prasad family, despite Jasmita, 15, and her brother Jasneel, 12, being Australian citizens who would be forced to uproot from school in suburban Sydney and move to a village in Fiji they have never visited if the family is to remain together.

The ethnic Indian family has been living in Australia for nearly 17 years and all three Prasad children were born at Randwick Women's Hospital. Three-year-old Jashwin is not yet an Australian citizen.

Jasmita, who attends Randwick Girls' High School, and Jasneel, who is at Mascot Public School, have Australian passports and the family's migration agent has warned the government it could knowingly be sending two Australians to a life of poverty and possibly homelessness in Fiji.

Jitend Prasad and his wife Joytika arrived in Australia in June 2000 shortly after the military coup in which George Speight overthrew the elected government of ethnic Indian prime minister Mahendra Chaudhry.

The Prasads say they were caught up in threats and violence by indigenous Fijians from a neighbouring village and applied for a protection visa shortly after arriving in Australia, claiming they would suffer discrimination and degrading treatment on the grounds of their ethnicity if they returned.

The Refugee Review Tribunal has found that the couple can safely return to Fiji but the family has asked the government to exercise discretion in keeping them together in Australia.

"If we have to go back to Fiji, where will our children live?" Mrs Prasad asked. "They have never stayed with anyone else. My daughter has been so upset that she wouldn't eat."

Jasmita, who wants to become a doctor, told Fairfax Media she would not move.

"We're Australians," she said. "We were born here and there is nothing for us in Fiji."

In a letter dated March 3, a Department of Immigration and Border Protection official told the Prasads that Mr Hawke had declined to use discretionary powers contained in the Migration Act, saying he did not believe it would be in the public interest to do so.

The Prasads could be sent to immigration detention or forcibly removed from Australia after April 4.

Migration agent Farnam Razzaghipour said in his two decades of experience, it was unusual for the federal government not to come down in favour of Australian citizens directly affected by a related immigration matter.

According to the law, the minister can use discretionary power if there are "strong compassionate circumstances that, if not recognised, would result in serious, ongoing and irreversible harm and continuing hardship to an Australian citizen or an Australian family unit, where at least one member of the family is an Australian citizen or Australian permanent resident."

"Forced removal of Mr and Mrs Prasad will cause irreparable harm and suffering to this family of five, two of whom are Australian citizens," Mr Razzaghipour said in a letter to Immigration Minister Peter Dutton.

The Prasads, who are financially supported by extended family in Australia, have not claimed any welfare benefits and, despite receiving Australian citizenship, Jasmita and Jasneel have not been given the right to access Medicare.

In a statement, the department said ministerial intervention was "not an extension of the visa process".

"The minister cannot be compelled to exercise his powers and he is not required to explain his decisions on any case," a spokeswoman said. "The minister only intervenes in a relatively small number of cases that present unique and exceptional circumstances.

"It would be inappropriate to confirm further details, including individual circumstances, relating to this case. People whose requests for intervention have been unsuccessful and who do not have other matters before the department are expected to depart Australia."