German Defense Minister Thomas de Maiziere is the target of federal auditors over the procurement of naval helicopters, Der Spiegel reported this weekend.

De Maiziere, who was heavily criticized this year over the bungled purchase of Euro Hawk surveillance drones, is again the subject of scrutiny, this time in connection with the purchase of MH90 light helicopters manufactured by Eurocopter, the German weekly reported Sunday.

Der Spiegel said the Federal Court of Auditors in Bonn had confirmed auditors are carrying out a probe of a March agreement struck by the German government and Eurocopter after months of negotiations in which the two sides agreed to a reduced number of helicopters, necessitated when Berlin announced a downsizing of defense forces in 2011.

Under the terms of deal struck by De Maiziere -- a close conservative ally of Chancellor Angela Merkel -- Germany agreed to buy 82 MH90s rather than 122 originally planned, with 18 set for the German navy to replace its aging fleet of Sea Kings and Lynx.

The deal for the navy choppers raised objections because it ended a planned competition in which the NH90 naval offshoot was to have competed with the Sikorsky H-92 Cyclone and the AgustaWestland AW101.

That has prompted the European Commission to launch an investigation of its own over possible violations of procurement laws, Der Speigel reported.

Despite the lower number of aircraft, their overall costs have decreased only slightly, triggering the audit. The court said it is studying the "financial impact of the number reduction/adaptation in the procurement of the Marine helicopter MH90."

"The MH90 is becoming the most expensive helicopter in the history of the (German armed forces)," Green Party budget expert Tobias Lindner told the publication.

Meanwhile, doubts about the suitability of the aircraft are growing.

"The MH90 is not the best aircraft for the needs of the Navy," Social Democratic Party defense expert Hans-Peter Bartels said, adding that if the problems with the helicopter continue to spiral, "the decision should be reconsidered."

The U.S. Army Aviation Corps concluded the rotorcraft have only "limited" suitability as a rescue helicopter, and are "not suitable" as combat escorts after extensive testing at Holloman Air Force Base in New Mexico.

The defense committee of the German Bundestag (the lower house of Parliament) in June halted the further procurement of all rotary wing assets for the German armed forces, citing budgetary reasons for the decision, the German online publication Aviation Update reported.

The MH90 audit comes only months after De Maiziere cancelled the $815 million purchase of Euro Hawk surveillance drones manufactured by Northrop Grumman after it was discovered the European Aviation Safety Agency would not allow them to fly in Europe due to safety reasons.

That episode, along with reports the defense ministry tried to cover up details of the bungled deal, brought calls for De Maiziere's resignation.

In response, the defense minister set up a task force headed by a military aviation authority and a defense board meant to monitor larger procurement projects, Der Spiegel said.