The European Parliament’s Green United Europeans/Nordic Green Left group Friday called for the resignation of Climate Action and Energy Commissioner Miguel Arias Cañete, following reports that he is under investigation by the EU’s anti-fraud watchdog OLAF.

Spanish news agency Europa Press Wednesday reported that Cañete is being investigated for possible tax evasion. A source told the outlet that OLAF will verify whether Cañete “declared everything that he had to declare” and whether he properly informed the European Commission.

The media report said the anti-fraud watchdog will conclude its investigation before the end of the year.

“Cañete must be expelled from our EU institutions as part of the clean-up,” said Miguel Urbán, a Spanish GUE/NGL MEP, in a press release. “The investigation into him by OLAF is not only a stain on the EU, but it undermines the credibility of democracy itself because of his public office and his duty towards our citizens.”

OLAF’s press office did not confirm the report, saying in an email to POLITICO that it had to “protect the confidentiality of any possible investigations and of possible ensuing judicial proceedings.”

A Commission spokesperson said no comments on OLAF investigations can be given, since it’s an independent body.

Last year, the name of Cañete’s wife was linked to the Panama Papers scandal. A stash of leaked reports detailed how clients of a Panamanian law firm sought to reduce or avoid taxes.

The Commission then said there was no conflict between the commissioner and his wife’s business, adding that her company has been “inactive for several years.”