* Daimler says is cooperating fully with probe
* Probe investigating ex-Merkel ally who joined Daimler
* Daimler says its executives acted correctly (Adds background on the nature of the investigation)
FRANKFURT, Nov 8 (Reuters) - Daimler executives are under investigation for suspicion of "granting undue advantage" to Eckart von Klaeden after Chancellor Angela Merkel's former aide joined the carmaker as a lobbyist, the Berlin prosecutor's office said on Friday.
"A probe into granting undue advantage is targeting executives at Daimler," a spokesman for the Berlin prosecutor said.
Daimler said it would cooperate with authorities and said it remained convinced that its executives acted correctly. The company declined to elaborate further due to the ongoing investigation.
Germany's WirtschaftsWoche reported earlier that the probe was targeted at Chief Executive Dieter Zetsche. Zetsche was not immediately available to comment on Friday.
Klaeden, a former treasurer of Merkel's Christian Democrats who spent the last four years in a senior chancellery role, said in May that he would quit the government after Germany's Sept. 22 national elections to take up the position of chief political lobbyist at Daimler. Klaeden was also not immediately available for comment.
German weekly magazine Der Spiegel, without citing any source, reported on Sunday that Klaeden, who was known to have met with Daimler representatives while still in politics, had access to three confidential government papers between January and May 2013 on the European Union's planned regulation of auto emissions.
Germany last month blocked an agreement among EU member states to cap car emissions, arguing the plan would cost jobs and hurt its premium carmakers BMW, Volkswagen's Audi and Mercedes-Benz, a unit of Daimler.
A spokeswoman for the Berlin prosecutors said on Sunday they had received an anonymous complaint filed against Klaeden.
"It's a completely normal procedure that prosecutors start investigations because an anonymous complaint was filed," Stuttgart-based Daimler said in a statement on Friday. "We have no doubts at all about the integrity of Mr. Klaeden." (Reporting by Edward Taylor. Editing by Jane Merriman)