DUESSELDORF/FRANKFURT (Reuters) - Innogy, Germany's largest listed energy group said it will continue with its advertising strategy despite plans by parent RWE and peer E.ON to break it up.

Listed to much fanfare in 2016 in Germany's largest share sale since 2000, Innogy spent a mid-double digit million euro sum on introducing its brand, it said. This implies an amount of about 40-60 million euros (£35.15-$52.72 million).

"We are not conducting our business any different in light of the agreement with regard to the planned transaction between RWE and E.ON," Innogy said in emailed comments to Reuters when asked whether ad spending would fall.

Innogy's advertising campaign, spread across television, radio and billboards in Germany's biggest cities, is handled by German agency Scholz & Friends.

At $4.07 billion, Innogy is Europe's fourth most valuable utility brand behind France's EDF (>> Electricité de France), Italy's Enel and Engie, according to consultancy firm Brand Finance.

Costs related to the carve-out and listing of Innogy have come into focus since RWE and E.ON last week announced a major restructuring coup that spells Innogy's end as a standalone company less than two years after it was created.

Despite the initial share price jolt some investors remain sceptical in light of the latest strategic shift, questioning whether previous splits had been necessary.

"A couple of years ago we were told that the way forward in utilities was networks, renewables and customers. That mantra seems to be easily thrown out of the door," Martijn Olthof, senior portfolio manager at APG Asset Management.

Shares in RWE were unchanged at 1533 GMT, while those of E.ON were 1 percent lower, with analysts at Investec calling Innogy's break up a "German fudge to the problems raised by the Energiewende".

(Editing by David Evans)

By Tom Käckenhoff and Christoph Steitz

Stocks treated in this article : Engie, Electricité de France, Enel, RWE, E.ON, Uniper SE, innogy SE