It was a questionable, controversial practice -- new doctors working 30 hours straight -- that had already been banned in 2011. But the U.S. government proceeded in October with the $9 million experiments anyway, to see if patient care was affected when doctors worked these extended shifts. Now, two advocacy groups are pushing back and have asked the government to halt these tests, citing “serious health risks” and highly questionable ethics.

Public Citizen and the American Medical Student Association wrote two letters Thursday to the Office for Human Research Protections, urging federal regulators to impose limits on how many consecutive hours residents can work and asking the U.S. Department of Health and Human Services to stop the experiments. It also wrote a letter to the Accreditation Council for Graduate Medical Education asking it to withdraw waivers for 16-hour shift limits that the council had granted hospitals for these trials. iCompare and First are the clinical trials that allow first-year medical residents to work at least 28 hours straight.

Advocates of longer shifts have said that extended hours for doctors in hospitals cut down on the number of hand offs between them and the possibility of injurious or deadly errors that can occur during those trades. But marathon shifts can also lead to sleep deprivation and brutal working conditions that make doctors more mistake-prone, critics of the practice have said.

“The trial — an experiment involving internal medicine residents and their patients without their consent — is highly unethical and fails to comply with federal regulations for the protection of human subjects involved in research,” Public Citizen and the American Medical Student Association said in their letter to the Office for Human Research Protections regarding the iCompare trial, in which dozens of major hospitals around the country are participating.

The organizations used similar language in their letter regarding the First trial. They also called for the 152 participating hospitals to be sanctioned and for both of the experiments to be investigated, arguing that they had serious design flaws that could lead not just to biased results but also to dangers for both patients and doctors.

“These trials are among the most unethical research studies I have ever seen,” Michael Carome, director of Public Citizen’s Health Research Group, said in a press release. They had not sought the voluntary and informed consent of residents who would be involved in the trials, he noted.

The First trial technically ended June 30, but waivers granted to the hospitals involved are not scheduled to expire until June 2016, meaning that even though the experiment is over, residents can still be required to work the extended shifts that the American Medical Student Association has said pose clear risks to doctors.