"The economy is firing on all cylinders, the upswing is entering a new boom phase," Timo Wollmershaeuser told Reuters in an interview, adding there were production bottlenecks and an over-utilization of capacities in practically all sectors.

He urged the next government to take the strong economic growth into account when considering more fiscal stimulus.

"If the economy continues to perform so well, it would be wise to postpone the planned tax cuts and implement them only gradually, ideally not until 2019 when the ECB is likely to turn off its money tap," Wollmershaeuser said.

He confirmed Ifo's growth forecasts for the German economy to expand by 2.6 percent this year and by 2.1 percent in 2019. "It could even be a bit more, there are more upside than downside risks to this forecast," Wollmershaeuser said.

(Reporting by Michael Nienaber,)