Development of a successor to the PlayStation 3 "is already under way", Sony executives confirmed today.

Asked to explain increased research and development (R&D) costs in the company's latest financial report, Sony executive vice president and chief financial officer Masaru Kato told investors it was a result of spending on the forthcoming NGP handheld and a "future platform".

"We have a portable, NGP, to be launched later this year, so we have development expenses to be incurred for this product," Kato said. "For the home equipment the PS3 still has a product life, but this is a platform business, so for the future platform – when we'll be introducing what product I cannot discuss that – but our development work is already under way, so the costs are incurred there."

It is the first official acknowledgement that Sony is doing any research or development on a successor to the PlayStation 3, but it is not known what Sony's plans are for the device.

Kato's comments contrast with previous statements by Sony Computer Entertainment head Kaz Hirai, who as recently as March claimed that "a near-future PS4 or next-generation home console is not something that we are even debating now." Hirai has consistently stressed that the PlayStation 3 would have a 10-year lifetime, and that Sony wasn't "even at the half-way point".

The shift in thinking and rhetoric may be a result of recently revealed plans by Nintendo to release a replacement for the Wii, codenamed Project Cafe, which is expected to be launched in 2012 and will be demonstrated at E3 next month. Unsubstantiated rumours also claim that Microsoft is working on a successor to the Xbox 360, and that studios including EA have already been provided with early development kits for the next Xbox.

However, even if Sony and Microsoft are prototyping the next generation of consoles, it could still be several years until they are ready to launch.