The names of British web users who have illegally downloaded copyrighted material from the web, and the number of times they have done so, must be logged by ISPs, according to Ofcom.
The measure is part of the Code of Practice, which was published by the watchdog last week, in a bid to fulfil the measures to tackle internet piracy set out in the Digital Economy Act, which was passed by MPs last month.
Ofcom confirmed that the Code of Practice will initially apply only to fixed-line ISPs with over 400,000 subscribers, meaning the UK's seven largest internet access providers; BT, TalkTalk, Virgin Media, Sky, Orange, O2 and the Post Office, will be required to conform to the code.
ISPs will have to send warning letters to web users suspected of illegal file-sharing. The details of those that have received three or more notifications in a year can be request by copyright holders in a bid to start legal action.
Ofcom also said it planned to "establish an independent, robust subscriber appeals mechanism for consumers who believe they have received incorrect notifications" as well as dealing with industry disputes and distributing the cost of enforcing the code.
"The code of practice forms part of a wider set of industry activity to tackle online copyright infringement including consumer education, the promotion of lawful alternative services and targeted legal action against serious infringers," Ofcom said.
The Digital Economy Act requires the code to come into force "no later than eight months from Royal Assent, including approval from the European Commission". As a result Ofcom says it expects the code to come into force in early 2011.
The watchdog said it will keep the government informed on the effectiveness of the code.