Qatar's World Cup sites will be inspected from next year by an international trade union which wants the deaths of all workers assessed by external coroners and for the causes to be published.

Qatar has come under fierce criticism over living and working conditions for workers since being awarded the 2022 World Cup in a contentious vote six years ago.

Qatar says only four stadium workers have died, with just one fatality the result of a work-related accident after a Nepali was hit by a water truck last month. The Building and Wood Workers' International, which will conduct labor and accommodation inspections with tournament organizers from January, wants more information published about deaths in the low-paid, migrant workforce.

"We have to know the cause, the actual medical legal cause," BWI general secretary Ambet Yuson told The Associated Press after signing the partnership with Qatar on Tuesday.

Yuson wants non-Qatari coroners to examine the bodies of workers and for death certificates to be published.

"We will propose this in the working group," Yuson said. "We really want to know what happened. We want to verify and investigate. They are committed to be open to us."

World Cup workers are covered by regulations that are more rigorous than the national laws, detailing how contractors must ethically recruit, promptly pay, and decently house them. But the BWI is concerned that the regulations only cover workers directly employed by the companies handed World Cup contracts, overlooking subcontractors who could be forced to live in cramped conditions.

"We have to look through the whole supply chain, through the subcontracting system," Yuson said. "There have already been reports that the big multinational construction companies have good facilities.

"Now we are interested in looking at the subcontractors. There is a possibility that many subcontractors are not complying. This is what we want to look at seriously — that the standards are applying not just to the main contractors but to all the level of subcontractors."

World Cup organizers said Tuesday that 36,000 people will be employed on its projects in the next year as eight stadiums are built.

"Our inspection and auditing processes will need to be bolstered to ensure we continue to deliver sustainable and meaningful progress for our workers," organizing committee secretary general Hassan Al Thawadi said in a statement. "While we have made a number of improvements in the last two years, from health and safety to accommodation standards, we recognize there is still work to be done."