By Darren Waters
Technology editor, BBC News, Texas
Internet Explorer is used by the vast majority of computer users
Microsoft is ignoring web standards and should use its position to promote competition among browsers, the chief technology officer at Opera has said.
The complaint comes as Mozilla, the makers of another rival web browser, declared the "browser wars" over at the South by Southwest festival in Texas.
Hakon Wium Lie, from Opera, said: "Microsoft has to make sure there is user choice when it comes to browsers."
Internet Explorer's newest version will be standards compliant, Microsoft says.
Mr Lie said Microsoft's platform dominance gave them an "obligation to promote competition".
His company has already complained to the EU that Microsoft is using its dominance to promote Internet Explorer over Opera and other browsers. And Google has lent its support to the complaint.
Mr Lie said he was concerned that Microsoft would use its Windows Software Update System to distribute the forthcoming new version of Internet Explorer to users.
"That system should be used for other browsers too, to ensure users have genuine choice.
Opera says Microsoft needs to promote browser competition
"We would be happy to channel Opera into that software update system," he added.
Mozilla's chief technology officer, Brendan Eich, told BBC News they would support any move to incorporate Firefox into the Windows Update System.
But Chris Wilson, platform architect of the Internet Explorer platform team, said adding other browsers to the automatic updates could confuse users.
He told BBC News: "It could be jarring [for users].
"The move form one browser to another is a bigger leap because they have different UI [user interfaces], different tenets and different missions," he said.
He pointed out that all the other browsers had their own automatic update systems.
He added: "Microsoft doesn't own the ecosystem - we don't own the OEM [original equipment manufacturer] channel.
"Other people can install things on there. I have had systems with other browsers pre-installed before."
Mr Lie said: "There is a choice for people who are conscious about it - they can download and install them.
"But there is still one dominant browser, Microsoft's Internet Explorer and most people don't care or don't know how to get other browsers.
"There is still room for more competition. Why does Internet Explorer have so many users when in the past it has been such a terrible browser.
"There are so many better options there," he added.
Mozilla Firefox has steadily increased its share of the web browsing market
Mr Lie said Microsoft had backtracked on a commitment to be standards compliant with Internet Explorer 8, because the browser would not use default support standards when used on intranets.
Mr Wilson said the company had done this to ensure web developers could continue to use Internet Explorer 7 on their pages while they updated them to Internet Explorer 8.
Mr Eich said the imminent release of Internet Explorer 8 would see an end to the "browser wars" with users split between the last three versions of Internet Explorer, Firefox 2, Firefox 3, Safari, Chrome and Opera.
Mr Wilson agreed the "wars" were shifting into an era of co-operation.
"It's certainly fair to say there is a lot better co-operation and focus on interoperability across all the browsers."
Microsoft has faced criticism for "going it alone" in areas such as security and when it acted to fix the problem of so-called click-jacking, which is a cross-scripting method of shifting users from one URL to others without their knowledge.
While the problem affects all browsers, Microsoft implemented a solution on its own.
Mr Wilson said: "You need to respond very quickly otherwise you are leaving users to hang out to dry. We looked at where we were in the [development] cycle and couldn't wait for another cycle to address click-jacking."
He told BBC News: "In security issues you have to get solutions deployed quickly. We are perfectly happy for other browsers to take that solution and build on it."