Its designers claim the Vaio P, aimed at people who want to surf the internet, edit documents and check their emails on the go, is the lightest eight inch netbook in the world.

They said it does everything that equivalent models of bigger sizes would do.

The Vaio P includes most features found on a laptop, from a webcam and GPS to a built-in 3G modem allowing users to go online by inserting a mobile phone sim card.

Its keyboard, unlike many other small laptops, is easy to use, according to reviewers.

A basic model is available at £849, but a netbook that operates faster and has more memory will cost £1,370.

Joshua Topolsky from the technology website Engadget is sceptical about whether many consumers will pay the asking price.

He said: "It simply costs more than other options. A cost which Sony want users to 'aspire' to pay.

"There are plenty of viable, less expensive options."

The launch of the Vaio P marks a significant change in direction by Sony, which last February warned that the growing trend for netbooks risked squeezing the industry's already-tight profit margins.

by:telegraph