Campaigners called on Qatar on Thursday to change its policy towards migrant labourers preparing for the 2022 World Cup following an investigation by British newspaper, The Guardian, alleging "modern-day slavery".
The report said dozens of Nepalese workers have died while working in Qatar in recent weeks, raising concerns about the Gulf state's preparations to host the tournament.
The International Trade Union Confederation (ITUC) told the newspaper that at current rates at least 4,000 migrant workers could die before the tournament kicks off.
Quoting documents obtained by the Nepalese embassy in Doha, the paper said thousands of Nepalese - the largest group of labourers in Qatar - faced exploitation and abuses amounting to "modern-day slavery".
Aidan McQuade, director of Anti-Slavery International told AFP the evidence was "certainly highly indicative of a brutal working environment which is not good for anybody."
The Guardian said it had found evidence of forced labour on a huge World Cup infrastructure project, although work has not yet begun on building the stadiums for the tournament.
It said some of the Nepalese men had alleged that they had not been paid for months and had had salaries held back to prevent them from fleeing, while a group of 30 had sought refuge in the Nepalese embassy to escape the conditions of their employment.
Some workers complained that employers had confiscated workers' passports and refused to issue identity cards while others said they had been denied access to drinking water despite the fierce desert heat.