Germany's federal auditors are looking into a helicopter deal concluded between the government and Eurocopter, a media report said Sunday, placing the defence ministry again in the spotlight after an earlier scandal over a botched drone deal.

Spiegel news weekly said the Federal Court of Auditors had been checking the contract to buy new marine helicopters since the summer due to the "financial consequences" from a reduction in the order.

Although 202 helicopters were originally ordered, their number was later dropped to 157 due to the need to make savings but the overall cost only fell by around three percent of the original price, the magazine reported.

Eurocopter is owned by European aerospace giant EADS.

A defence ministry spokesman criticised the Spiegel report as "a potpourri" of "already known and refuted allegations" and did not address the claim about the auditor court checking the deal.

Defence Minister Thomas de Maiziere, who is a close confident of Chancellor Angela Merkel, is expected to retain the portfolio in a new 'grand coalition' with the Social Democrats.

In the run-up to September's elections, he became entangled in allegations he mismanaged a now-scrapped unmanned surveillance aircraft project with costly consequences.