Mobile phone maker Sony Ericsson has bought software vendor UIQ the Symbian subsidiary that makes a user interface competing with Nokia's Series 60.

Sony Ericsson is by far the largest UIQ customer, and the move was welcomed as inevitable. "I can't imagine Symbian's other shareholders can have been too chuffed at effectively subsidising S-E's software development.," said Dean Bubley of Disruptive Analysis.

Although other handset makers have moved away from UIQ, Sony Ericsson hopes to bring them back, by setting UIQ up at arm's length and keeping it available to third parties - in a conscious mirror of Nokia's strategy with the more widely used Series 60 Symbian interface. "UIQ on Symbian OS will continue to be openly available, licensed on equal terms to all its licensees," said Sony Ericsson's release.

Users of Sony Ericsson's veteran P900 series of smartphones can expect a more solid future. The latest model of the phone - the P990 - was delayed, and changes to the user interface were unpopular with reviewers. Sony Ericsson has also been using UIQ in more mass-market products including the M6600 Blackberry-like phone, and the W950 high-end Walkman phone.

With UIQ in house, Sony Ericsson can be more competitive with Nokia; if it can also get other handset makers onto the phone, users will benefit from greater competition in the smartphone market.

Sony Ericsson did not announce the value of the deal, but promised to keep the company run as a separate subsidiary. The company is looking forward to improving features such as push e-mail, Internet browsing, end user personalisation, and enhanced music applications, according to Mats Lindoff, Sony Ericsson's chief technology officer.