Cambodia's strongman leader, Hun Sen, has approved a strategy to allow surrogacy-born babies with Australian biological parents to leave the capital, Phnom Penh.

The move will come as a relief for up to 70 Australian couples, most of whom faced financial and family hardships trying to get their babies home from the impoverished nation.

Some of the couples have been trying for months to get approval through Cambodia's corrupt and dysfunctional legal system for their babies to leave.

As a human crisis developed, fears were held for twins who are expected to soon be born prematurely, requiring high levels of neo-natal care.

"Such care is not always available in Cambodia, so the ability to transfer these cases to higher-care hospitals internationally will be vital," said Sam Everingham, global director of the Australian consultancy Families Through Surrogacy.

Chou Bun Eng, Cambodia's secretary of state with the Interior Ministry, said the measures would be temporary.

"The validity of the announcement will be for nine months and 10 days … if a baby is born after the date of the announcement, that's an abuse," she said.

Late last year, Cambodia's government declared that commercial surrogacy was illegal and would be treated as human trafficking, and cracked down on about 50 surrogacy operators in Phnom Penh.

Police arrested Australian nurse Tammy Davis-Charles, whose company, Fertility Solutions PGD, allegedly signed at least 20 surrogacy agreements in the country, most of them with Australian couples who paid $US50,000 per baby.

Ms Bun Eng said that under the exit strategy, biological parents would have to satisfy the requirements of Cambodia's criminal and civil laws, which stipulate that any newborn belongs to the birth mother.

The Australians will have to prove a biological link to the baby through DNA testing, as well as obtain the surrogate's approval for the baby to be handed over.

Similar strategies were implemented in Thailand after its military government cracked down on a booming surrogacy industry in Bangkok after the baby Gammy scandal.

Ms Bun Eng warned against biological parents attempting to bypass the Cambodian procedures by taking babies to Vietnam or Thailand, where the Australian embassies are reportedly granting documents for them to travel to Australia.

"We think this is against the law with ill-intended purpose," she said, adding that intending parents who do not come forward to use the exit strategy would face serious consequences.

"If they try to hide, they have no right to take the baby out," Ms Bun Eng told the Cambodia Daily newspaper.

The Daily quoted an unnamed surrogacy expert saying surrogates who have given birth in Cambodia have been obtaining Cambodian passports for the baby and then travelling to Vietnam with the biological parents.

Mr Everingham said the Cambodian government had been too slow in coming up with a strategy, which had "caused great stress to many Cambodian surrogates and their intending parents".

He said the announcement would be welcomed by "dozens of Cambodian surrogates and intended parents around the world, but particularly in Australia, who have been awaiting news on this issue for months".

Ms Davis-Charles, the mother of twins born through surrogacy, is in jail awaiting trial on charges that could result in her being sentenced to up to two years in prison.

Her lawyer, Chheang Sophoan​, said the investigation had closed and a judge had already submitted the case to a trial that is expected to be held in late April.

"If it drags longer, it could violate her rights," he said.

The Australian government has warned its citizens not to enter into surrogacy agreements in such countries as Cambodia, where no laws exist to cover the practice.

But surrogacy groups say some of the operators who have been chased out of India, Nepal, Thailand and Cambodia have now turned to Laos to set up businesses attracting foreign clients.