Microsoft has released the first new version of its Internet Explorer web browser in five years, adding features aimed at halting its sliding market share.

Explorer became the dominant browser for viewing the world wide web after it took on Netscape in the late 1990s. From less than 20 per cent market share in 1996, it grew to more than 80 per cent by 2000.

Microsoft released five versions in that time but there have been no new versions since Internet Explorer 6 in August 2001, leading to accusations that Microsoft has ceased to innovate due to the lack of competition.

IE6 was introduced to coincide with the launch of its Windows XP operating system and Internet Explorer 7 is timed for the release of Windows Vista, its new operating system, due in the next three months.

Microsoft has faced increasing competition from Firefox, a new open-source browser.

Microsoft’s market share has fallen from 93 per cent two years ago to an estimated 86 per cent in the US, with Firefox gaining 11 per cent, according to statistics firm WebSideStory.

Firefox was faster than Explorer and introduced features such as tabbed browsing, where several pages can be open at once. Version 2.0 is about to be released.

IE7 has tabbed browsing, improved printing and stronger security to defend against malicious attacks. However, security researchers warned of a new “hole” in the browser within hours of its release.