More than 40 humanitarian workers have signed an open letter to the Australian government criticising a new law that could put whistleblowers in jail for exposing the conditions at detention centres.

The Australian Border Force Bill which took effect on 1 July, allows for a jail sentence of up to two years for those who speak publicly about detention centres without the permission of the government.

CNN said John Paul Sanggaran, a doctor who used to work at an immigration centre on Christmas Island, an Australian territory in the Indian Ocean, is circulating an open letter addressed to Prime Minister Tony Abbott "challenging the department to prosecute" him and others for exposing the "deplorable state of human rights" for asylum seekers in the centres.

"We have advocated, and will continue to advocate, for the health of those for whom we have a duty of care, despite the threats of imprisonment, because standing by and watching sub-standard and harmful care, child abuse and gross violations of human rights is not ethically justifiable," the letter said.

CNN said a number of organisations, including the Australian Medical Association, the Royal Australasian College of Physicians, the Australian College of Nursing, the Australian Lawyers Alliance and several teachers' unions have also expressed their opposition to the new law.

"The new act essentially puts doctors in a dilemma when treating detainees and asylum seekers if they have concerns about the provision of their healthcare," The Australian Medical Association president Brian Owler said.

Owler told CNN that the new law covers anyone contracted to work in detention centres, including workers providing security or food services. "There is no clear reasoning why that's necessary," he said.

The Abbott administration has been pushing through strict laws for asylum seekers to stop them coming to Aussie shores. Since 2013, those who enter the country by sea cannot stay in Australia while their refugee claims are being processed.

They are transported to offshore detention facilities on Manus Island in Papua New Guinea or Nauru.

Australia's Minister for Immigration and Border Protection Peter Dutton however said that the bill will not suppress reports of human rights abuses.

"It will seek to investigate leaks of operationally sensitive information, however the public can be assured that it will not prevent people from speaking out about conditions in immigration detention facilities," Dutton said, according to CNN.

Thousands of migrants, mainly from Bangladesh and Rohingyas from Myanmar have been stranded in the Andaman seas with nowhere to go and limited supplies of food and water.