Migrant workers who built luxury offices used by Qatar’s 2022 football World Cup organisers have told the Guardian they have not been paid for more than a year and are now working illegally from cockroach-infested lodgings.

Officials in Qatar’s Supreme Committee for Delivery and Legacy have been using offices on the 38th and 39th floors of Doha’s landmark Al Bidda skyscraper – known as the Tower of Football – which were fitted out by men from Nepal, Sri Lanka and India who say they have not been paid for up to 13 months’ work.

The project, a Guardian investigation shows, was directly commissioned by the Qatar government and the workers’ plight is set to raise fresh doubts over the autocratic emirate’s commitment to labour rights as construction starts this year on five new stadiums for the World Cup.

The offices, which cost £2.5m to fit out, feature expensive etched glass, handmade Italian furniture and even a heated executive toilet, project sources said. Yet some of the workers have not been paid, despite complaining to the Qatari authorities months ago and being owed wages as modest as £6 a day.

By the end of this year several hundred thousand extra migrant workers from some of the world’s poorest countries are scheduled to have travelled to Qatar to build World Cup facilities and infrastructure. The acceleration in the building programme comes amid international concern over a rising death toll among migrant workers and the use of forced labour.

“We don’t know how much they are spending on the World Cup but we just need our salary,” one worker said after losing a year’s pay on the project. “We were working but not getting the salary. The government, the company: just provide the money.”

The migrants are squeezed seven to a room, sleeping on thin, dirty mattresses on the floor and on bunk beds, in breach of Qatar’s own labour standards. They live in constant fear of imprisonment because they have been left without paperwork after the contractor on the project, Lee Trading and Contracting, collapsed. They say they are now being exploited on wages as low as 50p an hour.

Their case was raised with Qatar’s prime minister by Amnesty International last November, but the workers have said 13 of them remain stranded in Qatar. Despite having done nothing wrong, five have even been arrested and imprisoned by Qatari police because the collapse of their employer left them without ID papers. Legal claims lodged against the former employer at the labour court in November have proved fruitless. They are so poor they can no longer afford the taxi to court to pursue their cases, they say.

“I earned no money,” said a 35-year-old Nepalese worker and father-of-three who said he had lost a year’s salary on the project. “If I had money to buy a ticket I would go home.”

Qatar’s World Cup organising committee confirmed it had been granted use of temporary offices on the floors fitted out by the unpaid workers. It said it was “heavily dismayed to learn of the behaviour of Lee Trading with regard to the timely payment of its workers”. The committee stressed it did not commission the firm. “We strongly disapprove and will continue to press for a speedy and fair conclusion to all cases,” it said.

Jim Murphy MP, shadow international development secretary, said the revelation added to the pressure on the World Cup organising committee after it promised to monitor workers’ welfare. “They work out of this building, but so far they can’t even deliver justice for the men who toiled at their own HQ,” he said.

Sharan Burrow, secretary general of the International Trade Union Confederation, said the workers’ treatment was “criminal”. “It is an appalling abuse of fundamental rights yet there is no concern from the Qatar government unless they are found out,” she said. “In any other country you could prosecute this behaviour.”

Contracts show the project was commissioned by Katara Projects, a Qatar government organisation under the auspices of the office of the then heir apparent, Sheikh Tamim bin Hamad al-Thani, who is now the emir. He also heads the supreme committee, the World Cup organising body. The committee is spending at least £4bn building new stadiums for the tournament, which has become mired in allegations of bribery, while there is disbelief at the prospect of playing the tournament in Qatar’s 50C summer heat.

Katara said it terminated its agreement with Lee Trading when it discovered the mistreatment of workers and “non-payment of wages”, and made efforts to repatriate those affected or find them new jobs. It said several workers had been compensated following court settlements. “If there are employees who were not repatriated, did not find employment or did not receive compensation, we would be happy to engage in any effort with the ministry of labour and ministry of interior to rectify the situation,” a spokesman said.

The problems for the Tower of Football workers are not isolated, despite Qatar’s pledges to monitor salary payments and abolish the kafala sponsorship system, which stops migrant workers changing job or leaving Qatar without their employer’s consent. In 2012 and 2013, 70 labourers from India, Nepal and Sri Lanka died from falls or strikes by objects, 144 died in traffic accidents and 56 killed themselves, the government’s own figures show.

Dozens more young migrant workers die mysteriously in their sleep from suspected heart attacks every summer.

The Reporters also discovered dozens of workers who had not been paid on several construction projects. They included 65 workers in a desert camp who had not been paid for several months and were living with dirty drinking water, filthy unplumbed toilets, no showers and sleeping eight to a room.

Another group said they were only being paid sporadically, there was sometimes no water in their housing and no electricity to power air conditioning.

This month, the Qatar Foundation, a state body, published a report examining trafficking, debt bondage and forced labour among migrant workers. It identified practices that contravene International Labour Organisation conventions on forced labour and UN anti-trafficking protocols, “widespread” non-payment of wages and bribery and extortion among recruitment agents and employers.

From January to the end of May this year 87 Nepalese workers died in Qatar, a death rate two-and-a-half times higher than that of British expats, new figures from the Nepal government reveal.

“We know there is much more to do,” said Abdullah al-Khulaifi, Qatar’s minister of labour and social affairs in a statement detailing progress on labour law reforms. “But we are making definite progress and are determined to build momentum.”