A new campaign led by the International Trade Union Confederation (ITUC) has asked sponsors of the Fifa World Cup to speak out against the 2022 tournament in Qatar.

The ITUC has written to major sponsors including Adidas, Russia’s Gazprom, Hyundai, Kia, McDonald’s, Budweiser, Coca-Cola and Visa to put pressures on the organisers because of poor working conditions.

The international trade union released a statement claiming that Qatar’s treatment of workers is “simply slavery”.

Letters have been sent to eight big sponsors urging them to use their position to put pressure on Fifa.

British newspaper The Guardian had reported in 2013 about bad labour practices on Qatar building sites amid the mounting controversy about Fifa’s decision to appoint Qatar to organise the 2022 World Cup Finals.

Qatar has promised to reform the treatment of migrant workers on Qatari building sites. The government commissioned an investigation by the international law firm DLA Piper and promised to implement recommendations listed in a report published in May 2014.

Human rights organisations, however, still accuse Qatar of dragging its feet on the reforms, saying not enough is being done to investigate the effect of working long hours in temperatures that regularly exceed 50C.