Swiss authorities have opened criminal proceedings against Sepp Blatter in a dramatic escalation of the corruption crisis engulfing football’s ruling body, Fifa.

The Uefa president, Michel Platini – the former European footballer of the year who was once Blatter’s protege but has latterly turned on him and was favourite to replace the Swiss as Fifa president – was also dragged into the web of allegations engulfing the organisation. Investigations centre on a payment of two million Swiss francs (£1.35m) made to Platini in 2011.

After arriving to question Blatter at Fifa’s opulent Zurich HQ and seizing his computer, the office of the Swiss attorney general said it had opened proceedings against him “on suspicion of criminal mismanagement” and “suspicion of misappropriation”.

Platini, who is lobbying to replace Blatter when he stands down in February, was questioned “as a person asked to provide information” in connection with claims that he received a “disloyal payment” from the Fifa president.

According to the attorney general’s office, the payment was made “at the expense of Fifa” for work allegedly performed between January 1999 and June 2002, when Blatter was in his first term as president and Platini, who helped him to win election, was a paid consultant.

However the payment was not executed, it said, until February 2011. That was three months after Qatar had controversially won the right to host the 2022 World Cup with the help of Platini and three months before Blatter was re-elected unopposed as president.

His victory came only after his only rival, the Qatari Mohamed bin Hammam, was forced to pull out amid bribery claims.

Last night Platini said in a statement: “Regarding the payment that was made to me, I wish to state that this amount relates to work which I carried out under a contract with Fifa and I was pleased to have been able to clarify all matters relating to this with the authorities.

“Today I also made clear to the Swiss authorities that since I live in Switzerland I am available to speak with them any time to clarify any matters relating to the investigations.”

Video: Investigative journalist Andrew Jennings says Sepp Blatter is lying when he denies knowledge of corruption within Fifa. Blatter, however, denies the allegations

The Swiss attorney general, Michael Lauber, has been pursuing a parallel investigation to the long-running inquiry instigated by the US Department of Justice that has already resulted in 14 people, including nine Fifa officials, being charged over what was alleged to be a $100m “World Cup of fraud”. Initially the Swiss inquiry focused on the process that led to the award of the 2018 World Cup to Russia and the 2022 World Cup to Qatar but its focus has since broadened. It has identified 121 suspicious banking transactions, seized properties in the Swiss Alps thought to have been used for money laundering and is trawling through 11 terabytes of data.

The feeling that the Fifa house of cards is collapsing was compounded last week when Jérôme Valcke, the Fifa secretary general and Blatter’s long-time right-hand man, was suspended by the organisation amid allegations that he had profited from the sale of black market tickets. Valcke denies the allegations.

Blatter, forced in May to promise to stand down following a dramatic wave of dawn arrests in Zurich, had been due to host a press conference when representatives of the Swiss attorney general’s office arrived at the end of an executive committee meeting described by one present as “routine”.

Other members of the Fifa executive committee at the meeting, which touched on a reform process that Blatter vainly hoped would salvage his reputation, were caught unawares as a planned press conference was first delayed and then cancelled.

As well as the allegations involving Platini, the attorney general’s office said it suspected that “on 12 September 2005 Mr Joseph Blatter has signed a contract with the Caribbean Football Union (with Jack Warner as the president at this time); this contract was unfavourable for Fifa.” It added: “On the other hand, there is a suspicion that, in the implementation of this agreement, Joseph Blatter also violated his fiduciary duties and acted against the interest of Fifa and/or Fifa Marketing & TV AG.”

Last week Lauber, at a joint press conference with the US attorney general Loretta Lynch, confirmed that its investigation had broadened to include a 2005 TV deal unearthed by a Swiss broadcaster in which Blatter appeared to agree to sell broadcasting rights for less than their market value to Warner.

Warner was among the 14 individuals indicted in May and is currently fighting extradition in his native Trinidad.

In May seven Fifa executives were arrrested in the lobby of the Baur au Lac hotel as American prosecutors outlined charges of money laundering, racketeering and fraud against 14 individuals including nine high-ranking football officials.

Of the 14 indicted in May, 13 have been arrested, of whom three have been charged in US courtrooms and 10 await extradition. Four more have already pleaded guilty, including the American former Fifa executive Chuck Blazer.

Blatter, who originally planned to cling to power after being re-elected days after the dawn raids, has promised to stand down in February at a special congress. Blatter’s US attorney, Richard Cullen, said the contract the Swiss attorney general claimed he signed in 2005 with the Caribbean Football Union was “properly prepared and negotiated by the appropriate staff members of Fifa. Certainly no mismanagement occurred.”