Weaknesses in the Internet Explorer programme have allowed hackers "to start and lock computers that have a Windows operating system", said BSI, the German government's internet security agency.
BSI specifically recommended against using versions 6, 7 and 8 of Internet Explorer on XP, Vista and Windows 7.
Thomas Baumgaertner, a Microsoft spokesman in Germany, has been on TV and in the media over the weekend, disputing the statement, saying: "these were not attacks against general users or consumers."
Despite this, Microsoft has also admitted in its own security advisory that it was "actively working with partners" to fix the problem.
The German government's warning is "quite unprecedented", IT security researcher Alan Stevens said in a BBC TV news interview.
Stevens compared the Internet Explorer risk to "having a window open in your house" and said Microsoft was "working like mad" to close and bolt that window.
Infosecurity notes that this is not BSI's first warning about an internet browser. In September of 2008, the agency launched a similar comment against Google Chrome, saying the web browser was distributed in an unfinished advanced version.
Industry reaction to the German government's statement has generated surprise from a number of IT industry players.
Trusteer, a web browser security specialist with banking clients that include the Santander Group, said advising internet users not to use Internet Explorer may not be the best solution to the problem of web browser security.
Mickey Boodaei, Trusteer's CEO, said that, what is needed is a high security – but light-weight – browser add-in that creates a secure environment between the users' keyboard and the website, so preventing man-in-the-middle, man-in-the-browser, phishing and similar attack methodologies.
The German government, he explained, should really be working to help internet users make their web banking sessions more secure, rather than steering users towards alternative browser software which may also have its fair share of security vulnerabilities.
The problem, he said, is that most web browsers have vulnerabilities and what is needed is a technology which is already available in the marketplace to make the communication session more secure, rather than simply advising users to switch devices.
"Owing to its higher market profile, Internet Explorer is tested more than other browsers by both the security and the criminal communities, resulting in more vulnerabilities being discovered. It's therefore important that the regulators understand this, and advise users accordingly", he said.