Australian parents have been left stranded overseas with their newborn babies, unable to bring them home, after a court ban on commercial surrogacy in Nepal.

Distressed parents said the health of their babies was at serious risk and that the children were "basically being held hostage" because local authorities refused to issue them exit visas.

"The longer this goes on, the bigger the risk becomes," said one man whose twins, born six weeks prematurely, have fallen ill after their supply of formula ran out.

"It's a matter of time until something drastic happens. I would hate for someone to die."

Commercial surrogacy is banned in Australia and under NSW law prospective parents cannot pay a surrogate, even for arrangements in another country.

Nepal previously allowed the practice as long as the surrogate was not Nepalese, but its Supreme Court suspended commercial surrogacy services on August 25.

Parents said Nepali immigration officials have since refused to issue exit visas for babies born through surrogacy, even when the process was started long before the ban.

Lisa McDonald* was recently forced to return to Sydney, leaving her newborn son, Sam*, in Kathmandu with her husband, after she ran out of vital medicine.

She has a disease of the immune system and the couple's biological child was carried by a surrogate.

"It was so hard to leave him and come back, it was torturous," she said. "All I know is I want him home."

Sam had to be rushed to hospital last week but transport is difficult because a dispute with neighbouring India has led to petrol rationing.

The Nepali government is also in upheaval after the adoption of a new constitution, a process that sparked deadly and ongoing protests.

"It's really dangerous," Ms McDonald said. "This is wrong, to be holding babies hostage like this. These are tiny babies. They just need to get them out."

Nick Martin* and his partner have been in Kathmandu for six weeks with their twins. The Sydney father said resolving the babies' status did not seem to be a government priority.

"We are distraught, absolutely distraught," he said. "We're effectively being kept captive in a country we don't know, where we don't speak the language. We just have no idea when we're going to be going home."

Mr Martin said about 25 Australians, as well as parents from several other countries, were in the same situation and many had other children and jobs to return to. There were "half a dozen Australian babies with passports ready to go right now," he said, and twice that number obtaining the necessary paperwork.

"They are Australian citizens," he said. "By law, they have freedom of movement. Irrespective of people's views on surrogacy, these children have been determined by our government to be Australian citizens and they deserve their human rights."

The director-general of the Nepali Department of Immigration, Kedar Neupane, said resolving the situation was a "priority" but with the current political uncertainty it could still take some weeks.

"We are very positive ... but we are waiting for the cabinet decision on how we depart the surrogate babies," he said.

Australia's Department of Foreign Affairs and Trade is providing consular assistance to affected families.

The Australian government was making representations to its Nepali counterpart "to address the issue of those families who already have children born in Nepal, and those with children currently in gestation," a spokesman said.

"We all want a solution that is humane and considers the best interests of the children, birth mothers and families."

The director of Families Through Surrogacy, Sam Everingham, said the lack of options for surrogacy and adoption at home meant Australian citizens were prepared "to take risks in foreign countries to have children".

"We need to have an urgent review of state-based laws to allow compensation to a surrogate in Australia," he said.

"We can't go on like this, having Australians jumping from country to country where they have no protections in place, just because [our governments] ... won't take this issue seriously."

* Not their real names