A Fifa vice-president has demanded that Qatar ensures payment for a group of migrant workers who fitted out offices being used by its 2022 World Cup organising committee after the Guardian revealed some have gone unpaid for 13 months.

Jim Boyce, Britain's representative on Fifa's 24-person executive committee, said he was very concerned about the situation after repeated assurances from the organising committee that working conditions for World Cup workers would be safeguarded. "If the supreme committee is now using offices built by these people, they should immediately take steps with the Qatar government to make sure they are properly paid for the work they have done," said Boyce.

The revelation that more than a dozen men who fitted out lavish offices in Qatar's football HQ have not been paid for up to 13 months came just days after Fifa's president, Sepp Blatter, and its secretary general, Jérôme Valcke, met Qatar's emir, Sheikh Tamim bin Hamad al-Thani, to discuss World Cup preparations and "the ongoing reforms of labour rights to ensure the welfare of migrant workers".

The workers from Sri Lanka, India and Nepal worked on a £2.5m fitting of the 38th and 39th floor of the Bidda tower in Doha, which houses Qatar's supreme committee for delivery and legacy for the 2022 World Cup. The contractor, Lee Trading, was commissioned directly by the Qatar government, but failed to pay the workers, some of whom did not receive even modest salaries of £6 a day for more than a year.

They are now working illegally from cockroach-infested lodgings while the World Cup organising committee occupies the offices, sparking widespread concern.

"They should pay these workers," said Bert Schouwenburg, international officer of the GMB trade union. "The Qatari government has buried its head in the sand for long enough. It is time to address the worst and most extreme exploitation of workers anywhere in the world that is now taking place right under its nose."

In April, Jim Murphy, the shadow secretary of state for international development, met Hassan al-Thawadi, the chief executive of Qatar's World Cup organising committee, to discuss the kafala labour sponsorship systems that prevent workers changing jobs or leaving the country without permission from their employer. "When I travelled to Doha, I met the Qatar 2022 organisers on the 37th floor of the Bidda tower," Murphy said. "They made promises about workers and the reform of the kafala system. The news that the Bidda tower workers themselves haven't been paid makes those promises sound pretty empty."

Amnesty International raised the plight of some migrant workers with Qatar's prime minister in November. Photograph: Pete Pattisson

Amnesty International came across the workers last year, before the Guardian established they had worked on offices used by the World Cup organisers. Last November, the human rights campaign group raised their plight in person with Qatar's prime minister, interior minister and labour minister. It wrote to the ministry of labour asking for the men to be paid, allowed to leave the country or find new jobs.

Nicholas McGeehan, Human Rights Watch's Qatar researcher, said: "If Qatar had announced some meaningful reforms, they would be able to defend themselves against these depressing revelations, because reforms need time to take effect in a sector beset by abuse and exploitation. … Qatar's inertia on labour reform should concern Fifa and their sponsors just as much as allegations of corruption in the bidding process."