The canny bit of underwear has been designed in Japan and has the ability to generate enough electricity to power an iPod or keep a mobile phone charged.

It works via a solar panel which can be worn around the wearer's stomach and therein lies the obvious problem – how is the sun going to reach the panel if the woman is respectably attired?

Yoshiko Masuda, a spokeswoman for makers Triumph International Japan Ltd, admitted: "It might be difficult to put it to practical use considering people usually cannot go outside without wearing clothes over it, and there may be few places like a balcony or a garden in your house where you can use it outside."

Aptly, the 'Solar Power Bra' comes in a fetching green colour and can be powered by solar or electrical energy.

At the Tokyo unveiling Yuko Ishida modelled the lingerie, with a flashing message board on her stomach reading "save the earth" whenever light hit the solar panel.

"It is very comfortable and I really feel involved in eco-friendly efforts as well," the model said about the feel of the bra.

Triumph has previously released other eco underwear in Japan, including launching a 'Chopsticks' bra to encourage people to use reusable metal chopsticks and a 'No Shopping Bag' bra which doubles up as bag.