Harrison said Toyota was "not so far" from selling the second-generation model, with the third generation arriving within a decade.

As with all automakers selling in Europe, Toyota needs to progressively reduce carbon dioxide emissions from its new-vehicle fleet to comply with increasingly tougher targets mandated by the European Union.

"There is no perfect technology to meet this task to succeed," Harrison said. "We are preparing various alternatives and will let our customers decide which form of electrification suits them."

Harrison said Toyota's hybrid vehicles will help it hit the EU's CO2 reduction goal for 2020. Toyota has the lowest average CO2 of any mainstream automaker, as ranked by JATO Dynamics.

Toyota sold 480,000 hybrids last year in its European region, which includes Russia, with the technology accounting for 46 percent of sales. Looking at just Western Europe, that figure rose to 60 percent. "It's limited by supply for the second year running, not demand," Harrison said.

Harrison said Toyota has cut the cost of hybrid technology 75 percent since launching the first Prius in 1997. The car is now on its fourth generation. "Our next-generation hybrid technology will be more affordable still," he said.