The media regulator has today (June 26) published a draft Code for consultation that would require internet service providers, such as BT and Sky, to warn customers that they are facing allegations of online piracy.
Ofcom also said that the measures will attempt to encourage customers to download music and films through legal channels.
The watchdog was required to produce the Code under the Digital Economy Act, which was controversially pushed through in the final days of the last Labour government in 2010.
The code will initially cover ISPs with more than 400,000 fixed-line broadband customers. This currently includes BT, Everything Everywhere, O2, Sky, TalkTalk Group and Virgin Media - covering 93% of the UK retail broadband market.
These ISPs will be ordered to send letters to customers, at least a month apart, informing them when their account is connected to "reports of suspected online copyright infringement".
For any customers that receive three letters or more over a 12-month period, anonymous information about their account activity can be passed on request to copyright owners, such as music record labels or Hollywood studios.
BT and TalkTalk have previously attempted to challenge the legislation, saying that it will not tackle the problems of piracy and instead force them to 'police' the internet.
There have been concerns that innocent customers could be targeted in the approach, as pirates may hack into unsecured wireless networks to illegally download material without being connected to the crime.
But Ofcom stressed that it would ask ISPs to clearly explain the steps subscribers can take to protect their networks from being used to infringe copyright.
The letters will also apparently contain information on where consumers can go to access licensed content on the internet.
Customers retain the right to challenge any allegation of infringement through an independent appeals body set up by Ofcom.
They will have 20 working days to respond to the allegations, but Ofcom has removed the ability to appeal on "any grounds they choose", meaning it will now only accept grounds specified under the Digital Economy Act.
Anyone wishing to appeal the claims outlined in a warning letter must also pay a £20 fee, which consumer groups have warned could hit people on low-incomes and prevent them from challenging "unfair allegations".
The process of gathering evidence of potential infringement used by copyright owners must now be pre-approved by Ofcom before it can be used.
Ofcom will report regularly to the government on the effectiveness of both the Code and these broader initiatives from copyright owners.
"These measures are designed to foster investment and innovation in the UK's creative industries, while ensuring internet users are treated fairly and given help to access lawful content," said Claudio Pollack, Ofcom's consumer group director.
"Ofcom will oversee a fair appeals process, and also ensure that rights holders' investigations under the Code are rigorous and transparent."
The Digital Economy Act also includes other measures for the government to tackle online copyright infringement, including the requirement of ISPs to throttle the bandwidth connections of suspected copyright pirates, as well as temporarily suspend accounts and block internet access entirely.
However, those measures can only be considered after the new Code has been in force for at least 12 months, and would require further legislation to be approved by MPs.
Ofcom said that it will now consult on its revised Code. Subject to that and further review by the European Commission, it will be laid before Parliament around the end of 2012.
Ofcom expects that the first customer notification letters will not be issued until early 2014.