The call came after 11 women jailed for agreeing to carry a client's baby were released from prison.

The Southeast Asian nation has seen an uptick in commercial surrogacy after the practice was banned in Thailand in 2015, and has since been scrambling to draft a law to stamp out the trade.

In the meantime, dozens of surrogates have been charged under human trafficking laws and face up to 20 years in prison - a scenario that must change under the new law, said Chak Sopheap, head of the Cambodian Center for Human Rights (CCHR).

"The effect of the law should be to focus on the perpetrators and agents of surrogacy, who are often men, not the women who carry the children," she said.

"The possibility that these women were coerced or driven by poverty to become surrogates is high."

Surrogates told the Thomson Reuters Foundation they were offered $10,000 to carry a baby, more than six times the average annual salary in a nation where one-third of the population lives on the poverty line.

Family pressures, often brought about by excessive debt, can drive young women into surrogacy, women's rights experts said.

The release on bail last month of 11 surrogate mothers - some of whom gave birth in detention - follows that of 32 in December who were carrying babies for Chinese clients.

All were freed on the condition that they raise the babies as their own, but they still have human trafficking charges and potential 20 year prison sentences hanging over them.

"They agreed to not sell the babies, so we released them. But they remain under the supervision of the judge," Chou Bun Eng, deputy head of the National Committee for Counter Trafficking, told the Thomson Reuters Foundation.

"The law will follow them. In cases (where) they sell, they will be sent back to prison."

While no details of the new law have been made public and there is no timeframe for its introduction, Bun Eng indicated that surrogate mothers will be treated at the very least as criminal accomplices.

"They cooperate with the traffickers, so they are involved in the crime," she said.

A spokesman for Cambodia's Justice Ministry referred questions about the drafting of the law to the Women's Affairs Ministry, whose spokesman could not be reached.

Ros Sopheap, director of the charity Gender and Development for Cambodia, said that surrogacy should be outlawed in Cambodia, at least for now, as the safety of procedures could not be guaranteed.

Regardless, she said, new laws would likely be ineffective in a market fuelled by poverty.

"As long as demand is there, secret networks will continue to operate," she said.

Cambodia told the United Nations in June the new law would "protect women from exploitation and ensure that the rights of any children born through surrogacy are protected".

But CCHR's Sopheap said that the government had yet to provide clarity on how these protections would work, leaving those already engaged in surrogacy in limbo.

"This lack of clarity has driven surrogate mothers into hiding, and increasingly dangerous and precarious positions, for fear of unknown repercussions from the authorities," she said.