The International Labour Organisation on Friday accused Myanmar of "unprecedented" use of forced labour, and gave the ruling junta until the end of July to stop prosecuting whistle-blowers and release those detained.
At the United Nations agency's annual conference, its 178 member states also set an end-October deadline for Myanmar to agree to setting up a credible mechanism for dealing with forced labour complaints. It left open the option of referring Yangon to the world court if the deadlines are not met.
Although forced labour is officially outlawed in the former Burma, critics of the military which has ruled the country since 1962 say the army frequently obliges people to do unpaid work - often in areas where it is fighting rebels.
Myanmar told a three-week conference it was working to wipe out the practice through co-operation with the agency and also announced a moratorium on prosecuting those who report abuses.
An ILO report adopted by consensus on the final day of the conference cited an "unprecedented gravity of the forced labour situation in Myanmar".
In unusually strong language, it declared that it was "unacceptable to the ILO that a member state not only tolerated such practices, but was itself responsible for them." The ILO has been demanding Myanmar eradicate forced labour since 2000, in line with ILO conventions banning the practice, which it has ratified.
Pledging to work with the ILO to wipe out the practice, Myanmar announced a moratorium on prosecuting those who report abuses. It also released Su Su Nwei, an activist jailed for reporting two village leaders who used forced labour. But the ILO report said that despite limited progress, "there was every reason to believe that widespread and very serious abuses persisted".
The ILO said Myanmar's junta should provide further details on the prosecutions moratorium and extend it to cover prosecutions it said were now under way in the town of Aunglan.