Major sponsors Adidas, Sony and Visa on Sunday demanded that FIFA thoroughly investigate corruption allegations over Qatar's 2022 World Cup bid, piling pressure on football's rulers over the scandal.
The three make up half of FIFA's top level sponsors and account for hundreds of millions of dollars in World Cup revenues.
FIFA's corporate backers rarely speak out on the controversies that regularly hit international football.
But their statements are a sign of the growing worries over allegations that former Qatari football boss Mohamed bin Hammam paid millions of dollars in bribes to secure support for Qatar's deeply controversial victory in a 2010 FIFA vote.
Adidas in particular expressed concern on the impact of football's image. Sony said the accusations have to be "investigated appropriately."
But FIFA marketing director Thierry Weil played down their statements.
"We are in constant contact with our commercial affiliates, including Adidas, Sony and Visa, and they have 100 percent confidence in the investigation currently being conducted by FIFA's independent Ethics Committee," he said in a statement.
"Our sponsors have not requested anything that is not covered by the on-going investigation by the Ethics Committee," he added.
FIFA investigator Michael Garcia, a former US federal prosecutor, is to finish his inquiry into the 2018 and 2022 World Cup votes on Tuesday. But his report is not expected until mid-July, when the World Cup finals finish.
Adidas said in a statement that it was "confident that the matter is being dealt with as a priority".
The company highlighted its "long-term and successful partnership with FIFA" but added: "The negative tenor of the public debate around FIFA at the moment is neither good for football nor for FIFA and its partners."
Sony was reported by The Sunday Times as saying: "As a FIFA partner, we expect these allegations to be investigated appropriately."
It added: "We continue to expect FIFA to adhere to its principles of integrity, ethics and fair play across all aspects of its operations."
- strong ethical standards expected -
Visa was equally outspoken.
"Visa does not take part in the administration of sport," said a statement released by the credit card giant.
"Our expectation remains that all of our partners maintain strong ethical standards and operate with transparency.
"We understand FIFA is taking this matter seriously and we will continue to monitor its internal investigation. We expect FIFA will take the appropriate actions to respond to the report and its recommendations."
Qatar has strongly denied allegations reported by The Sunday Times that bin Hammam paid more than $5 million (3.6 million euros) in bribes to win support ahead of the 2010 vote in Zurich.
Allegations of skullduggery have surrounded Qatar's bid ever since its shock victory.
The tiny Gulf state beat the United States, Australia, Japan and South Korea, despite a FIFA technical report which warned the searing temperatures during June and July posed a health risk.
The Qatar 2022 Supreme Committee for Delivery and Legacy insists that it won the bid "on its merits."
It has also said bin Hammam played no "official or unofficial role" in the bid.
The Sunday Times, which this week detailed bin Hammam's meetings with key officials ahead of the FIFA vote.
The paper alleged bin Hammam was invited to visit Russia's then prime minister Vladimir Putin to discuss "bilateral relations in sport" in October 2010.
It also said bin Hammam helped arrange talks on a major gas deal between Thailand and Qatar during a visit to Doha by the president of the Football Association of Thailand, Worawi Makudi.
- 'there are huge bribes' -
Bin Hammam was on FIFA's executive committee but resigned in 2012, shortly before being banned for life from football administration by FIFA's ethics committee.
Argentine football legend Diego Maradona joined the chorus of criticism against FIFA.
"There are huge bribes" in the world football governing body, Maradona, now based in the United Arab Emirates, told Abu Dhabi daily, Al-Ittihad.
"Those behind them must be held accountable, especially in regards to the latest events related to awarding Qatar the 2022 World Cup.
"Where has this money gone, who received it, and why," must be investigated, he said, adding that he had repeatedly denounced, "in vain, cases of bribery within FIFA."
Maradona also criticised UEFA president Michel Platini, who voted for Qatar's bid, saying he had "surrendered" to such irregularities.
Platini has strongly denied being influenced to back Qatar. The former French international has said a re-vote for the 2022 World Cup should be held if corruption allegations are proven.