In evidence to the All Party Internet Group, the Internet Service Providers Association (ISPA) said the issue was of fundamental importance to ISPs and required immediate clarification.
"We would therefore recommend to the Government that the Crown Prosecution Service be encouraged to launch a test case under the Computer Misuse Act as soon as possible," ISPA said in a written submission to the group.
The Act should be modified as a "matter of urgency," if it is found wanting, it said.
The companies are concerned that under the Act, the police may have no straightforward way of prosecuting some types of electronic attack.
The police said they often have to use non-IT related laws to bring prosecutions against denial of service attackers, a factor that can sometimes make prosecutions more difficult and time consuming.
The police have also urged the Government to review sentencing for computer crimes. Len Hynds, head of the National High-Tech Crime Unit, said he would like to see tougher sentences for section 1 offences, which cover unauthorised access. Such a move would bring more computer crimes under the remit of the unit.
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