A SENATE investigation has uncovered dozens of credible reports of medical neglect and poor conditions in immigration detention centres across the United States. 

Detainees have been denied insulin, left without medical attention for days and forced to compete for clean water, the investigation found.

The report, released by Georgia Democratic Senator Jon Ossoff, is the second in a series of inquiries into alleged human rights abuses within the system. 

It builds on an August review detailing mistreatment of children and pregnant women, drawing on more than 500 reports of abuse and neglect between January and August.

The latest findings document over 80 credible cases of medical neglect and widespread complaints of inadequate food and water, provision, which Senate investigators said point to systemic failures of federal oversight.

According to the report, one detainee suffered a heart attack after being denied medical care for days, while others said inhalers and asthma medication were withheld or prescriptions delayed for weeks.

Detainees also described meals being too small for adults, milk that was sometimes out of date and water that smelled foul or appeared to make children sick.

Mr Ossoff said the findings expose “a deeper failure of oversight,” adding: “Every human being is entitled to dignity and humane treatment.”

National Immigration Project regional attorney Stephanie Alvarez-Jones said one of her clients at Louisiana’s Camp J facility had been left partially paralysed after being denied a prescribed medical device and placed in segregation.

“He was not able to get up and get his food, to shower by himself or to use the bathroom without assistance,” she said.

“So he had to lay in soiled bedsheets because he wasn’t able to get up.”

Ms Alvarez-Jones said the guards had insinuated to the man that they believed he was faking his illness.

Amica Centre for Immigrant Rights senior attorney Amelia Dagen said detainees at a Baltimore holding site had gone without proper food or clean water.

She is working on a lawsuit against the Immigration and Customs Enforcement and Removal Operations Baltimore Field Office, as well as officials in charge of national immigration enforcement efforts.

“This is 100 per cent a problem of [authorities’] own making,” she said. 

“They are setting themselves these quotas, removing discretion to release people and trying to arrest numbers of people that are just impractical … fully knowing they don’t have the ability to hold these people.”