A prisoners rights group called for the boycott of an international Buddhist conference in Myanmar next month because of the detention of an estimated 300 monks by the military regime.
The fourth World Buddhist Summit due to take place in December has already been hit by the pull-out of its main sponsor in a blow to a government trying to promote religious tourism.
The report by the Thailand-based Assistance Association for Political Prisoners (AAPP) out later this week cites new accounts of brutal interrogations of monks over the last 16 years.
Monks, widely respected in Myanmar where 85 percent of the population are Buddhist, have been stripped of their robes, beaten inside jails and sent to labour camps, according to the report: "Burma (Myanmar's former name): A land where Buddhist monks are disrobed and detained in dungeons".
Many monks have been jailed under a law designed to suppress dissent and are seen as posing a danger to the junta's rule because of links with the pro-democracy movement, according to the group.
It says many of the monks were given only perfunctory trials before being jailed for terms up to life.
"Torture is still going on," said AAPP joint secretary Bo Kyi. "They don't get good enough medical care, water or sanitation."
The report, based on interviews with more than 20 monks released from custody, focuses on the period after the crushing of pro-democracy riots in 1988 when monks were among the leaders. It says at least 100 monks have been arrested since 2003.
The AAPP called on the regime to release an estimated 300 monks and a couple of nuns among the country's 1,400 political prisioners, according to the group's sources in Myanmar. Amnesty International in its 2004 report said more than 1,350 political prisoners remained imprisoned.
The AAPP, which plans to deliver the report to the UN, foreign embassies in Thailand and religious groups, also called on worldwide Buddhist organisations to boycott any religious events hosted by the regime.
The military authorities have denied the existence of political prisoners in Myanmar and are trying to promote religious tourism to the "Land of Pagodas" to help its ailing economy suffering under international sanctions.
The internationally isolated regime has built a new convention hall and spruced up temples in preparation for next month's summit but its main sponsor, Japan's Nenbutsushu sect, has already pulled out.
Most participants have refused to attend after the junta last month sacked its premier General Khin Nyunt and put him under house arrest for corruption, according to the organisers.
They said it could no longer use the summit to spread its message of world peace and called on Myanmar to cancel the event. However Yangon has said it planned to press ahead with the conference on December 9-11.
The military has ruled Myanmar since a coup in 1962. The opposition, headed by Aung San Suu Kyi, won elections in 1990 by a landslide but has not been allowed to rule.