The government has proposed sharply increasing penalties for computer crimes, which are taking a heavy financial toll on UK businesses.

The Police and Justice Bill would amend the Computer Misuse Act of 1990, a Home Office spokeswoman said today. It would increase the maximum penalty for unauthorised modification of a computer from five years to 10 years in jail, a provision that would cover all forms of DDoS (distributed denial-of-service) attacks, she said.

If passed into law, those convicted of unauthorised access to a computer could face up to a two-year prison sentence, up from six months.

"Over the past 18 months there have been a lot of high-profile DoS attacks, which have in turn been accompanied by extortion requests against UK online bookmakers," the spokeswoman said.

The National Hi-Tech Crime Unit has estimated that e-crime costs UK-based companies with more than 1,000 employees £2.4bn annually. Of 200 companies that participated in the survey, 90 percent reported that they had experienced unauthorised access to their networks, while 89 percent had been victims of data theft.

The amendments would also bring the UK in line with commitments to the Council of Europe's Convention on Cybercrime in 2001 and the European Union's Framework Decision on Attacks Against Information Systems, both of which focus on stronger measures against e-crime, she said.

The bill has been introduced to the House of Commons.