Tens of thousands of unregistered Rohingya refugees, many of whom have lived in Bangladesh for decades, have been forced into makeshift camps where they are being left to starve to death, the report by Physicians for Human Rights says.
"It is unconscionable to leave this vulnerable population stateless and starving," said Richard Sollom, PHR director of research and investigations.
Described by the United Nations as one of the most persecuted minorities on Earth, thousands of Rohingya from Myanmar's northern Rakhine state stream across the border into Muslim-majority Bangladesh every year.
Bangladesh recognises 28,000 Rohingya as registered refugees, who live and receive aid at an official UN camp in Kutupalong. This figure is a fraction of the 200,000 to 300,000 unofficial refugees, according to government estimates.
The report said the crackdown is an apparent attempt to dissuade any more refugees fleeing to Bangladesh ahead of elections in Myanmar later this year.
The police are "systematically rounding up, jailing or summarily expelling these unregistered refugees across the Burmese (Myanmar) border in flagrant violation of the country's human rights obligations," the report said.
Up to 10,000 unregistered Rohingya, many of whom have lived in Bangladesh for years, have moved to the makeshift camps since January, local police say.
The crackdown has "quarantined" the unregistered refugees in the camps, which surround the official UN-run facility, and the report said they were effectively "an open air prison."
"This confinement, coupled with the Bangladeshi government's refusal to allow unregistered refugees access to food aid, presents an untenable situation: refugees are being left to die from starvation," it said.
The PHR report follows two other reports, one by lobby group the Arakan Project and one by Medecins Sans Frontieres (Doctors Without Borders), which also criticised the crackdown.
"The European Union is very concerned at the humanitarian situation. For those with no access to any food programme, the situation is grim," MEP Jean Lambert, who led a recent visit to the refugee camps, told AFP.
The Bangladeshi government on Sunday dismissed media reports relating to undocumented Myanmar nationals in Bangladesh as "baseless and malicious."
It views the Rohingya as economic migrants and maintains they must be repatriated.
"We are arresting illegal Rohingya and pushing them back over the border. It is an ongoing operation," said Rafiqul Islam, chief of the local police in Kutupalong, on theMyanmar border.