The Qatari government and the Qatar Football Association are suing former German FA (DFB) president Theo Zwanziger for libel, German newspaper Bild has reported.
Zwanziger has been critical of the awarding of the 2022 World Cup to the Arab nation and in June, after having left his DFB post in 2012, said Qatar was "a cancer on world football" in an interview with the hr-Info radio station.
The 70-year-old, a member of the FIFA executive committee from 2011 to 2015, was reported as saying he was "relaxed" about the legal threat.
On Thursday, Bild said officials in Qatar had decided to sue for libel.
In a statement, part of which was published by the paper, the officials described Zwanziger's words as "unacceptable."
Zwanziger, the statement said, had not backed his "rabble-rousing criticism" with facts, and although Qatar was open "to objective criticism" his words had gone too far.
It said freedom of speech "on no account" justified libel.
In a brief statement to Spiegel Online, Zwanziger said he was on holiday and added: "Should there be a lawsuit, I will face it calmly."
Zwanziger has become known for his forthright views and has also has been critical of FIFA president Sepp Blatter, who announced his resignation earlier this month.
The development comes soon after world football's governing body announced initial plans to elect Blatter's replacement.
FIFA's executive committee will meet in Zurich on July 20 to decide when -- at some time between December and February -- the election to find Blatter's successor should be held.
Earlier, politicians from 28 European nations, meeting at the European Parliament in France, voted on a resolution calling for Blatter to speed up his announced resignation and let FIFA appoint an interim leader.
FIFA, which has no obligation to heed the parliament, said it was "perplexed" by the resolution.
The parliament urged its member states -- which do not include Switzerland, the home of FIFA's headquarters -- to "cooperate fully with all ongoing and future investigations on corrupt practices within FIFA."