Action is to be taken against firms involved in scams that divert dial-up internet connections to premium rate numbers without users' knowledge.
Users have unwittingly run up huge phone bills
The UK watchdog for premium rate phone services, Icstis, is shutting down all such services that operate without its permission.
The action follows a surge in complaints from members of the public.
Thousands of UK surfers are believed to have been hit by the scam, some facing phone bills of up to £2,000.
So far Icstis has barred 11 companies and is looking at shutting down a further 33.
It follows an earlier decision to license all companies wanting to run premium rate dialler services.
There are legitimate companies who offer services such as adult content, sports results and music downloads by charging a premium rate rather than by credit card.
HOW TO SPOT LEGITIMATE SERVICES
There should be clear call costs
On-screen terms and conditions
Contact details for the company
Confirmation box showing you agree to download software
On-screen clock showing running total of costs
Automatic cut-off if cost reaches £20
Icon to show dialler is installed
Most of these require users to download a piece of software, known as a dialler, which temporarily switches the user from their usual service provider to a premium rate number for the duration of the visit to the website.
Only a small minority of these are believed to be fraudulent.
"This is a further stage in our action to stamp out rogue diallers," said Icstis director George Kidd.
"Any company we find running a dialler without our permission will be cut off immediately," he added.
Companies must now satisfy stringent conditions, including clear terms and conditions, information about how to delete diallers and responsibility for customer refunds.
Icstis also called on the phone networks that distribute premium rate numbers to play their part.
"They have a duty to carry out thorough checks on those they give numbers to. Billing phone companies have the systems to identify suspicious call patterns and should take action before their customers unknowingly run up huge bills," Mr Kidd added.
Some of the diallers originate from abroad, and Icstis has notified phone networks that they should cut off any dialler services using international numbers as none of them are legitimate.
There are around 80 phone companies in the UK that can hand out premium rate services. About half of dozen of these are believed to be responsible for the vast majority of complaints and any that Icstis is concerned about will be referred to the telecoms watchdog Ofcom.
The telecoms giant BT has welcomed the new strict approach.
Gavin Patterson, BT's group managing director, said it would help its customers avoid huge unwanted bills.
"We believe that taking down these unlicensed premium rate internet diallers will help to minimise the number of victims," he said.
BT has taken its own action to combat the menace of rogue diallers, blocking 1,000 numbers allegedly associated with the scam.