Qatar's construction frenzy ahead of the 2022 World Cup is on course to cost the lives of at least 4,000 migrant workers before a ball is kicked, the International Trade Union Confederation (ITUC) has claimed.

The group has been scrutinising builders' deaths in the Gulf emirate for the past two years and said that at least half a million extra workers from countries including Nepal, India and Sri Lanka are expected to flood in to complete stadiums, hotels and infrastructure in time for the World Cup kickoff.

The annual death toll among those working on building sites could rise to 600 a year – almost a dozen a week – unless the Doha government makes urgent reforms, it says.

The ITUC has based the estimate on current mortality figures for Nepalese and Indian workers who form the bulk of Qatar's 1.2 million-strong migrant workforce, the large majority of whom are builders.

While it admits that the cause of death is not clear for many of the deceased – with autopsies often not being conducted and routine attribution to heart failure – it believes harsh and dangerous conditions at work and cramped and squalid living quarters are to blame.

The stark warning came after a Guardian investigation revealed that 44 Nepalese workers died from 4 June-8 August this year, about half from heart failure or workplace accidents.

Workers described forced labour in 50C heat, employers who retain salaries for several months and passports making it impossible for them to leave and being denied free drinking water. The investigation found sickness is endemic among workers living in overcrowded and insanitary conditions and hunger has been reported. Thirty Nepalese construction workers took refuge in the their country's embassy and subsequently left the country, after they claimed they received no pay.

The Indian ambassador in Qatar said 82 Indian workers died in the first five months of this year and 1,460 complained to the embassy about labour conditions and consular problems. More than 700 Indian workers died in Qatar between 2010 and 2012.

Qatar World Cup construction 'will leave 4,000 migrant workers dead'

abrahiml5