FIFA leader Sepp Blatter said Wednesday he was "surprised" by the resignation of top corruption investigator Michael Garcia over the handling of his inquiry into the Qatar and Russia World Cup bids.

"I am surprised by Mr Garcia's decision. The work of the Ethics Committee will nonetheless continue," Blatter said in a statement released following the decision of the US lawyer to quit as head of FIFA's ethics committee investigatory committee.

The FIFA president added the inquiry into the Qatar and Russia World Cups "will be a central part of the discussions" at a FIFA executive committee meeting in Marrakech, Morocco, on Thursday and Friday.

Jerome Champagne, a former FIFA official who has said he will stand against Blatter for the FIFA presidency next year, called Garcia's resignation "a step backwards" for the governing body.

"We needed to know what happened before and after the December 2, 2010 vote. Today more than ever we need to know," Champagne said in a statement.

"When will the facts be known fully, transparently and above all without suspicion?" he added.