Qatar said an EU investigation into a corruption scandal in the European Parliament could negatively affect gas supplies and Doha's ties with Europe.
A statement issued by a Qatari diplomat criticized Belgian authorities for using inaccurate information, EuroActive reported.
Eva Kaili, a Greek member of the European Parliament, is one of four people charged with corruption after raids that uncovered at least 1.5 million euros in cash. It is suspected that they came from Qatar.
The scandal erupted at a time when many European countries are turning to Qatar for supplies of liquefied natural gas.
Moroccan interests are also under scrutiny in the investigation, according to media reports.
The statement stressed the close relationship with Belgium.
Qatar believes it has been unfairly singled out because its sentiments were influenced by other accusations made against the wealthy Gulf state over its hosting of the World Cup.
Qatar has already had one diplomatic confrontation with Germany in recent months. Doha summoned the German ambassador after the interior minister questioned whether Qatar could host the World Cup because of its treatment of foreign workers.
