A report from Human Rights Watch says World Cup stadium workers in six cities had not been paid wages for months and worked in temperatures as low as -25 degrees Celsius without sufficient breaks.
Human Rights Watch (HRW) on Wednesday said it had documented cases where workers building venues for Russia's 2018 football World Cup had been left unpaid, made to work in dangerously cold conditions, or suffered reprisals for raising concerns.
The sport's world governing body, FIFA, announced a monitoring system in 2016 for labour conditions at Russia's World Cup stadiums, and says the system has helped to improve labour standards.
But in a statement accompanying the New York-based campaign group's report, HRW's associate Europe and Central Asia Director Jane Buchanan said:
"Construction workers on World Cup stadiums face exploitation and abuse, and FIFA has not yet shown that it can effectively monitor, prevent, and remedy these issues."
TRT World spoke with journalist Håvard Melnæs who first exposed the exploitation.
FIFA said that "while incompliances with relevant labour standards continue to be found – something to be expected in a project of this scale – the overall message of exploitation on the construction sites portrayed by HRW does not correspond with FIFA's assessment."
A spokesperson said this assessment was based on quarterly inspections conducted by independent experts and trade union representatives.
FIFA also said that it was Russian authorities who "ultimately have the responsibility to protect human and labour rights on their territory and ensure that construction companies are held accountable."
Russia is set to host the World Cup next summer in 12 stadiums spread across 11 cities, including Moscow, St Petersburg, Kazan and Sochi.
These four cities are set to host matches in the Confederations Cup, a two-week tournament kicking off Saturday that will feature world champions Germany, various regional champions and the host country.
Russia's World Cup organising committee was not available for immediate comment.
In May, Deputy Prime Minister Vitaly Mutko told TASS news agency that construction works at the stadium in St Petersburg were in compliance with FIFA requirements and that workers' rights were not being violated.