Mr Clarke, 50, helped Virgin Net win the Internet Service Provider of the Year Award for 1997. He will now become managing director of "new media and interactive services" at Mirror Group, the division that already runs the UK's fifth most popular website.
Mirror Group has big hopes for its website, which registered 20 million "hits" in January against 2m for the same month last year. More than 8m of those are on the Sporting Life site, and the division also has an on- line betting service developed with the Tote and called TotalBet.
Mr Clarke started his career at Hewlett Packard and had stints with Digital and Compaq before joining Richard Branson's Internet venture in June 1997. Mr Clarke's first task will be to launch the Mirror's free Internet service provider in the next few months, which is still under development.