Ericsson has announced it will intervene to prevent Nokia from gaining control of Symbian Ltd - the company that controls the mobile device operating system.

A spokesman for the company confirmed that the company will exercise its right to increase its stake in Symbian. Ericsson and five other shareholders have pre-emption rights in which they can purchase the same percentage of shares put up for sale as their holding in the overall company.

Last month, Psion announced its intention to sell its 31.1 percent stake in Symbian - something that would give Nokia 63.3 percent and control over the company. That deal came less than six months after Motorola sold its 19 percent stake to Nokia and Psion. The Psion deal was approved by its shareholders - after some argument - last week.

However, the Ericsson spokesman said the company would "act as a team" with Sony Ericsson in exercising their purchase rights, which would bring Nokia's overall stake in Symbian down to 46.7 percent. Ericsson CEO Carl-Henric Svanberg has said that he wants to prevent Symbian from becoming "a Nokia platform".

Nokia is keen to prevent its purchases from being seen as aggressive however, with a company spokeswoman stressing a speech by CEO Jorma Ollila in which he stated that he would be happy to see other Symbian shareholders exercise their rights. Nokia has also been talking publicly about how it intends to continue running the OS as an independent entity.

Among Symbian shareholders are Ericsson with 17.5 percent, Sony Ericsson with 1.5 percent, Matsushita (7.9 percent), Samsung (5.0 percent) and Siemens (4.8 percent).

Symbian was launched in 1998 by several large handset manufacturers as a venture to control the development of operating system software for smart phones. It competes, among others, against Microsoft, which is trying to extend its dominant position in the PC operating system software market to mobile devices.