Two of Fifa's leading sponsors, Coca-Cola and McDonald's, have demanded that the president, Sepp Blatter, step down immediately in the face of an ongoing corruption crisis.

The dramatic intervention from two of Fifa's longest standing sponsors hugely increases the pressure on the 79-year old after Swiss prosecutors last week opened criminal proceedings against him. Blatter, who is accused of making a "disloyal payment" of €1.76m to Uefa president Michel Platini in 2011 and handing a World Cup TV contract to the disgraced former Fifa vice-president Jack Warner for below its market value, immediately reiterated his determination to remain in post.

In what was clearly a co-ordinated strategy financial services company Visa, a top tier sponsor with a contract through to the 2022 World Cup, also added its weight to the calls for Blatter to resign immediately.

Budweiser owners Anheuser-Busch InBev later became the fourth major sponsor to call for Blatter’s head. “It would be appropriate for Mr Blatter to step down as we believe his continued presence to be an obstacle in the reform process,” said a spokesman.

“While Coca Cola is a valued sponsor, Mr Blatter respectfully disagrees with its position,” said a statement.

Coca-Cola, one of five top-tier Fifa global partners, said: "For the benefit of the game, the Coca-Cola Company is calling for Fifa president Joseph Blatter to step down immediately so that a credible and sustainable reform process can begin in earnest."

The soft drinks giant, which has made sponsorship of the World Cup and the Olympics a key part of its global marketing strategy since the 1970s, added: “Every day that passes, the image and reputation of Fifa continues to tarnish. Fifa needs comprehensive and urgent reform, and that can only be accomplished through a truly independent approach.”

McDonalds, a second-tier sponsor, said: “The events of recent weeks have continued to diminish the reputation of Fifa and public confidence in its leadership.

“We believe it would be in the best interest of the game for Fifa president Sepp Blatter to step down immediately so that the reform process can proceed with the credibility that is needed.”

Since US prosecutors dramatically charged 14 individuals, including nine current or former Fifa officials, with offences including money laundering, racketeering and fraud in May, Blatter and the organisation he has shaped in his own image have been under huge pressure.

Blatter won re-election just days after a series of Zurich dawn raids but promised to stand down in early June. Since then, he has clung to his plan to step down in February, in the seemingly vain belief that he will able to salvage some of his reputation in the meantime by introducing long overdue reforms.

But the intervention of two of the sponsors who have previously called for an independent reform process, and warned they will walk away if one is not put in place, dramatically raises the stakes.

Jaimie Fuller, of NewFifaNow, said it was a major development. "Never before have we seen a sponsor of an international sports federation take such drastic action as to call for an independent reform commission, let alone demand the president step down in the face of a criminal investigation," he said. "The drastic nature of the call stresses the extreme problems faced by Fifa and should show everyone how it is teetering on the abyss."

Fifa's malaise has only increased in the past week as Platini, the Frenchman who was favourite to succeed Blatter in February, has been drawn into the spiralling crisis. In the absence of the secretary general, Jerome Valcke, who has been suspended pending an investigation into claims that World Cup tickets were resold above face value, the organisation is effectively being run by lawyers on a day to day basis.

Michel Platini was questioned under Swiss law as "someone between a witness and the accused" and has failed to come up with a satisfactory explanation as to why the €1.76m payment was made nine years after his contract with Fifa ended. Earlier this week, he told AFP that Blatter had said Fifa did not have the money to pay him at the time and he had not got around to claiming the cash until February 2011, two months before Blatter was re-elected. At the time, Blatter was facing a challenge from Mohamed Bin Hammam, who was later forced to withdraw in the face of bribery allegations.

But the scale of the crisis facing Fifa is emphasised by the fact that if Blatter was to stand down, the long-standing Fifa vice president Issa Hayatou – himself the target of various allegations down the years – would step up.

Although some of Fifa’s sponsors, who collectively contribute more than $1.5bn over each four-year World Cup cycle, have previously called on Fifa to restore its credibility, Coca-Cola in June became the first to advocate wholesale reform. The Guardian revealed then it had sent a letter to the International Trade Union Confederation following a campaign under the banner New Fifa Now to try to force sponsors to take responsibility for driving change at Fifa. The campaign intensified in the wake of the meltdown that followed the indictment of 14 football executives by the US department of justice on corruption charges.

The ITUC general secretary, Sharan Burrow, said then Coca-Cola had set a benchmark and called on other sponsors to follow suit. She said: "It's now time for the other sponsors such as Visa, Adidas and McDonalds to take a stand against corruption and put the game back on track." Adidas, tightly interwoven into the Fifa story since Horst Dassler helped lever Blatter into power, has a contract until 2022. It has previously noted its concern at the ongoing swirl of negative headlines surrounding world football's governing body but has stopped short of demanding action.

Meanwhile, the Swiss Attorney General, Michael Lauber, has said that its investigation – which began as a probe into the awarding of the 2018 and 2022 World Cups – has not even reached half time. Swiss prosecutors have already seized property in the Alps suspected of being linked to money laundering, as well as 11TB of data and 121 suspect banking transactions. In the US, the Attorney General, Lorretta Lynch, has also warned that further arrests are likely as the extradition process continues against those seized in May.

(Guardian service)