THE HAGUE: A Dutch labour union is threatening FIFA with legal action if it does not step in to halt what the union has branded "modern slavery" in the construction of venues for the 2022 World Cup in Qatar.

Dutch union FNV says it wants "FIFA to accept its responsibility and end exploitation of workers" in stadium construction ahead of the tournament.

The gas-rich emirate is expected to spend tens of billions of dollars before the November-December 2022 tournament kicks off, preparing eight new and renovated stadiums and related projects such as transport links and accommodation.

Qatar is relying heavily on workers from south Asia who are tied to the "kafala" system of sponsorship common in Gulf nations, which critics say exposes migrants to exploitation.