The Fifa and Uefa presidents, Sepp Blatter and Michel Platini, have issued almost simultaneous statements denying any wrongdoing relating to the £1.35m paid to Platini in February 2011, for which Blatter is subject to a Swiss criminal investigation.

Lawyers for Blatter said he will remain as Fifa president despite the investigation by the Swiss attorney general, Michael Lauber, into a suspicion that the money paid to Platini was a “disloyal payment”. Both men stated that it related to work Platini did at Fifa as Blatter’s adviser – which finished nine years earlier, in 2002. Blatter and Platini are also subject to investigation over the same payment by Fifa’s ethics committee, meaning both could imminently be suspended, which would scupper Platini’s candidacy to be elected Fifa president when Blatter steps down in February.

Blatter’s lawyers, Lorenz Erni, based in Zurich, and Richard Cullen, in the US, said in their response: “President Blatter spoke to Fifa staff today and informed the staff that he was cooperating with the authorities, reiterated that he had done nothing illegal or improper and stated that he would remain as president of Fifa.”

Platini and Blatter sought to clarify that the £1.35m, which the Frenchman confirmed he was paid in February 2011, was for work he legitimately did at Fifa. In a letter of explanation sent to all Uefa’s 54 national football associations, including the English FA, Platini said he acted as special adviser to Blatter. Blatter’s lawyers described it as “a valuable employment relationship” and said “the payments were valid compensation and nothing more.”

Lauber is examining whether the £1.35m was a “disloyal payment” made by Blatter “at the expense of Fifa,” which is understood to mean an alleged breach of Blatter’s fiduciary duties to act in the best interests of his employer. Blatter was interrogated as a defendant in Zurich on Friday, while Lauber stated that Platini was interviewed “as a person asked to provide information”.

Blatter and Platini both emphasised that the £1.35m was paid properly through the Fifa books and Platini said he declared it to the relevant authorities in Switzerland. The money was “the final outstanding amount” owing to him, Platini said, although he did not explain why it took nine years to be paid. Nor did he refer to the close timing between receipt of that £1.35m and his decision not to stand against Blatter in the 2011 presidential election but to support him instead.

“I wish to clarify that for the period 1998 to 2002 I was employed by Fifa to work on a wide range of matters relating to football,” Platini wrote. “It was a full-time job and my functions were known by all. The remuneration was agreed at the time and after initial payments were made, the final outstanding amount of 2m Swiss francs was paid in February of 2011.”

Blatter also denied any criminality relating to a 2005 TV contract granted to Jack Warner, the former president of the Caribbean Football Union, for which Lauber is also investigating the Fifa president. In his statement on Friday Lauber said Blatter is the subject of criminal proceedings relating to these two matters “on suspicion of criminal mismanagement and – alternatively – misappropriation”.

Platini also highlighted that he was not interviewed by Lauber as a suspect “but simply in my capacity as a person providing information”. That status in Switzerland does not put a person beyond possible suspicion, however. Defined at article 178 of the Swiss code of criminal procedure, a “person asked to provide information,” includes “a person who cannot be excluded as the perpetrator of or as a participant in the offence under investigation.”

Platini said he will not be making detailed statements “as a matter of respect”, but intended to clear his name.

“I am aware that these events may harm my image and my reputation and by consequence, the image of Uefa, the organisation of which I am proud to be president,” he wrote. “For these reasons, I wish to use all my energies to ensure that any issues or misunderstandings can be resolved as soon as possible.”

The English FA is understood to be still officially supporting Platini to become Fifa president but will discuss the affair at its board meeting on Wednesday.