Blatter denies 'illegal or improper' conduct, to remain FIFA president until February

Sepp Blatter will not go gentle into that good night.

The FIFA president told staff members Monday he would not step down prematurely and that he's done "nothing illegal or improper," despite an ongoing criminal investigation into his affairs.

The 79-year-old is due to give up his post of 17 years in February, after announcing in the summer he would resign following the arrests of several FIFA officials.

Related: Blatter returns to FIFA headquarters amid Swiss investigation

"President Blatter spoke to FIFA staff today and informed the staff that he was co-operating with the authorities, reiterated that he had done nothing illegal or improper and stated that he would remain as president of FIFA," a statement from Blatter's attorney read.

Among the fresh charges against Blatter from the Swiss Attorney General are criminal mismanagement and misappropriation - including a supposed "disloyal payment" of two million Swiss francs in 2011 to UEFA president Michel Platini for work performed between January 1999-June 2002.

Related: UEFA chief Michel Platini addresses role in FIFA controversy

Platini, who has only been cited as a witness in the Swiss probe, has denied any wrongdoing.

The statement from Blatter's attorney continued:

President Blatter on Friday shared with the Swiss authorities the fact that Mr. Platini had a valuable employment relationship with FIFA serving as an adviser to the president beginning in 1998. He explained to the prosecutors that the payments were valid compensation and nothing more and were properly accounted for within FIFA including the withholding of Social Security contributions.

Investigators interrogated Blatter on Friday following a two-day meeting of the executive committee, and also searched his office at FIFA headquarters.

It's only the latest of many scandals over the last year to hit world football's governing body. Earlier this month, FIFA's ethics committee suspended Blatter's right-hand man, secretary general Jerome Valcke, after a series of allegations about his involvement in a scheme to sell World Cup tickets for greater than face value.