After making an offer of more than £200m to buy British telecoms software firm Symbian, Nokia is clubbing together with its rivals to create an open source mobile platform.

Nokia currently owns about 48 per cent of shares in Symbian and has tabled a cash offer of around €264m, (£209m) to buy the remainder. Nokia has received irrevocable undertakings from other shareholders including Sony Ericsson, Panasonic and Siemens and is expecting the same from Samsung, clearing the way for the acquisition.

Nokia expects the deal to close in the fourth quarter of this year, subject to regulatory approval and customary closing conditions, at which point all Symbian staff will become Nokia employees.

The deal coincides with the formation of the Symbian Foundation, which includes Nokia, AT&T, LG Electronics, Motorola, NTT DOCOMO, Samsung, Sony Ericsson, STMicroelectronics, Texas Instruments and Vodafone. The companies are coming together to try and create an open source mobile platform, based on the Symbian system, which may present a viable rival to the Android platform being developed by Google and the Open Handset Alliance.

Nokia chief executive Olli-Pekka Kallasvuo said: "This is a significant milestone in our software strategy. Symbian is already the leading open platform for mobile devices. Through this acquisition and the establishment of the Symbian Foundation, it will undisputedly be the most attractive platform for mobile innovation. This will drive the development of new and compelling, web-enabled applications to delight a new generation of consumers."

Symbian chief executive Nigel Clifford added: "Our vision is to become the most widely used software platform on the planet and, indeed, today Symbian OS leads its market by any measure. Today's announcement is a bold new step to achieve that vision by embracing a complete and proven platform, offered in an open way, designed to stimulate innovation, which is at the heart of everything we do."