Labour abuse remains "rampant" in Qatar despite some reforms introduced since the Gulf Arab state won the right to organise the World Cup five years ago, Amnesty International said.

Qatar, one of the wealthiest countries in the world which is preparing to host the FIFA World Cup in 2022, has been widely criticised for its treatment of migrant workers, especially in the construction industry.

The gas exporter denies exploiting workers and announced labour reforms in May last year, but Amnesty says these changes have not gone far enough.

Amnesty said that under Qatar's "kafala", or work-sponsorship system, foreign workers are still required to seek their employer's consent to change jobs or leave the country, putting them at the mercy of their employers.

Qatar's Labour Ministry declined to comment on the statement. A ministry official has previously dismissed similar reports by NGOs as aiming to "create negative publicity about Qatar abroad".