The long-running feud between Sun Microsystems and Microsoft gained new intensity today as Microsoft retaliated against a series of full-page advertisements placed in major daily newspapers last week.

The ads invited customers to "demand that Microsoft include the Java platform in their XP operating system" and gave moves from some quarters to injunct the release of the software an extra impetus. Hitting back at Sun, Microsoft issued a press release Thursday in which it described Sun's tactics as "unparalleled hypocrisy." Microsoft claims it's Sun's fault that XP will ship without Java support and cites a court ruling which imposed significant restrictions on the software giant's use of the technology. Sun sued after Microsoft produced an "enhanced" version of Java which included a number of non-approved extensions designed to specifically target its Windows operating system. It was claimed that these extensions were a breach of the contract under which the product had been licensed to Microsoft. It was also alleged that Microsoft's move threatened the very "write once, run anywhere" tenet on which Java was built by encouraging developers to write Windows-specific Java programs. Thursday's response from Microsoft claims that "the Microsoft [Java] virtual machine has a long history of outperforming other virtual machines and offers the best real world compatibility of any virtual machine... It is also the only virtual machine that offers an integrated applet browsing experience with Internet Explorer"