Major sponsors Visa and Coca-Cola pressed FIFA to help improve labour conditions in Qatar as Amnesty International accused the 2022 World Cup host of failing to deliver on promised reforms for migrant workers.
"We continue to be troubled by the reports coming out of Qatar related to the World Cup and migrant worker conditions," credit card giant Visa said Wednesday, adding that it had expressed its "grave concern" directly to football's top body.
Coke said it was also pressing FIFA to demand more labour reforms from Qatar, after fresh accusations from rights group Amnesty that labourers in the tiny oil-rich country were dying in their hundreds.
"We expect FIFA to continue taking these matters seriously and to work toward further progress," the company said.
Their statements, which come after similar criticism from sponsor Adidas, are the strongest indication yet that high-profile commercial backers are becoming increasingly uneasy over the treatment of migrant workers in Qatar.
FIFA is due to hold a meeting later this month that could see a resolution put forward to remove the World Cup from the country -- the first ever awarded to the Middle East -- because of the slow pace of labour reforms.
World football's governing body said it would continue "to urge the Qatari authorities to accomplish reforms".
"FIFA has repeatedly urged publicly and with the highest authorities in Qatar that fair working conditions for all workers in Qatar are imperative," it said.
But Amnesty warned that "without prompt action, the pledges Qatar made last year are at serious risk of being dismissed as a mere public relations stunt to ensure the Gulf state can cling on" to the event.
In the latest of a string of reports on migrant worker "abuse", the rights group said Doha had failed to deliver reforms in key areas such as pay, the "kafala" system that blocks workers from leaving the country and curbs on changing employers.
Some 440 migrant workers from India and Nepal -- the two countries with the largest number of migrants working on World Cup projects -- died in 2014, Amnesty said, citing their governments' figures but without detailing how they were killed.
"Qatar is failing migrant workers," said Mustafa Qadri, Gulf migrants researcher at Amnesty.
"Last year the government made promises to improve migrant labour rights in Qatar, but in practice, there have been no significant advances.
"The lack of a clear roadmap of targets and benchmarks for reform leaves serious doubts about Qatar's commitment to tackling migrant labour abuse," he said.
- 'Promising little, delivering less' -
The release of Amnesty's report, "Promising little, delivering less: Qatar and migrant labour abuse ahead of the 2022 Football World Cup," caps a turbulent week for Doha.
On Monday, it emerged that a BBC journalist invited to Qatar to examine the living conditions of workers building infrastructure for the World Cup had been arrested and held without charge.
Qatar has been repeatedly criticised for the poor working conditions of as many as one million migrant workers in the small, oil-rich Gulf country.
Facing searing international condemnation, Doha pledged in May 2014 to reform some of its more contentious labour laws but has so far failed to live up to its promises.
Earlier this month Abdullah bin Saleh al-Khulaifi, the minister of labour and social affairs, said he was "90 percent" certain the kafala system would be replaced by the end of 2015.
He added that the wage protection system would be up and running by mid-August as well as improvements to workers' accommodation.
But Amnesty said that with the number of migrant workers in the country expected to more than double, reforms to labour conditions were becoming increasingly vital.
Amnesty listed nine "fundamental" areas for reform and said Doha has managed only "limited progress" in five, and none at all in four.
It criticised Qatar for not meeting a target of having 300 labour inspectors in place by the end of last year and for the slow introduction of an electronic wage protection system.
"With Qatar's construction boom continuing and the migrant worker population set to expand to 2.5 million, the need for urgent reform is more pressing than ever," said Qadri.