Prosecutors in Berlin on Tuesday said they had dropped a probe against Daimler Chief Executive Dieter Zetsche, investigating whether the carmaker had "granted undue advantage" to a former aide of Chancellor Angela Merkel by hiring the aide.

Prosecutors launched a probe in November 2013 looking at whether Daimler had acted properly when it hired Eckart von Klaeden, a former treasurer of Merkel's Christian Democrats, as chief political lobbyist at Daimler.

"There were insufficient grounds for taking the matter further; the investigation has been dropped," a spokesman for the prosecutor's office said on Tuesday.