Larry Ellison, the multibillionaire chairman and chief executive of Oracle Corporation, mounted a sustained and sometimes humorous attack on Microsoft during his speech at the Comdex computer trade show in Las Vegas.

Mr Ellison, head of the world's largest supplier of computer database software, launched his first attack on Microsoft in Paris in 1995, when he said the PC was a "ridiculous" device that would be replaced by the simplified "network computer".

Microsoft, based in Redmond, responded recently by trumpeting the fact that its much cheaper Sequel Server database outperformed Oracle in an industry-standard banking benchmark test called TPC-C. Mr Ellison claimed Oracle performed better with typical applications and was more reliable.

"They're telling everyone Microsoft is very fast, albeit only for one application, and not for very long. We'll pay you $1m if we don't triple the performance of any Microsoft website [with Oracle 9i], except for running TPC-C," a clearly irritated Mr Ellison told the audience.

Both companies have increased the level of "trash talking" recently, and Microsoft's chief executive, Steve Ballmer, mocked Mr Ellison before the speech.

"Larry's been talking about ideas that have gone nowhere for years. How long has he been talking about the [network computer]? Six years, seven years? Where did it go? Nowhere," said Mr Ballmer.

Although his attacks on the PC made headlines, Mr Ellison's credibility has been damaged by the commercial failure of numerous alternative "network computers" and "information appliances" while PC sales have continued to grow to about 140m a year.

According to US research company International Data Corporation only 11m information appliances were sold in 1999, and almost two thirds of those were handhelds such as Palm electronic organisers.

Mr Ellison said that he had modified his views, and he was now in favour of standard configurations of all types of computer, large or small.

"It's a fundamental mistake the computer industry has made to only do custom configurations," said Mr Ellison.

Although users liked to choose their own hardware and software, this made every computer unique, and there were too many variations for anyone to test properly.

The war of words between Oracle and Microsoft looks likely to continue. Microsoft staff handed out mugs before Ellison's talk which were printed with instructions for negotiating discounts, such as: "When Oracle salesman pitches $5m of overpriced software, glance down at mug."