Austrian former racing driver Niki Lauda on Sunday accused German carrier Lufthansa of trying to "destroy" the Niki airline which he founded.

Niki -- formerly a unit of now bankrupt Air Berlin, and most recently operated by Lufthansa -- was grounded last Wednesday after applying to open insolvency proceedings.

The move came after Lufthansa abandoned plans to buy Niki, a holiday airline with 21 aircraft, together with large parts of Air Berlin because of EU competition concerns.

Lauda, 68, a former Formula One champion, had said last week he was potentially interested in again acquiring the airline he sold to Air Berlin in 2011.

But he has now charged that Lufthansa was effectively blocking the sale of Niki because it "wants to destroy" it, in comments to Bild am Sonntag newspaper.

Under EU rules Lufthansa would have to hand the leased aircraft to a potential investor, but the report said it had bought up many of its aircraft.

"Without aircraft, the airline has no value," Lauda said.

"If there is no new investor, the take-off and landing slots are divided among the remaining airlines at the respective airports.

"That's how Lufthansa gets what it wants, and for free."

A Lufthansa spokesman denied the claim and told the newspaper the airline was in compliance with the rules.

Air Berlin triggered bankruptcy proceedings in August after losing a cash lifeline from its biggest shareholder, Etihad Airways, and was grounded in October.

The European Commission said Wednesday that Lufthansa's offer to buy 81 aircraft from Air Berlin's 140-plane fleet plus Niki for 210 million euros ($250 million) posed "clear risks to Austrian, German and Swiss consumers and to effective competition".

In Germany, complaints have multiplied that Lufthansa had hiked ticket prices since the demise of the country's second biggest airline.

There had been "a significant increase in complaints about ticket prices," the head of the consumer protection federation, Klaus Mueller, told national news agency DPA.

"We see that many people are paying a lot more than they used to," he said.