Ofcom has unveiled its findings into how the Digital Economy Act could block websites that infringe on copyright.
The communications watchdog has concluded that, although it's technically possible for ISPs to block sites, that there are privacy issues and little likelihood of an effective framework for action to be taken.
Ofcom's report backs up what Business Secretary Vince Cable is expected to say later on Wednesday: that blocking plans are unworkable.
The report – which is available as a PDF – looks at the different ways in which sites can be blocked and then if there is a feasible and fair framework for doing this.
The report highlights privacy concerns and cost with some methods of blocking - such as deep packet inspection – points to the likelihood of people circumventing restrictions and even raises the spectre of the potential need to penalise search engines for making it easy to find copyright infringing files.
However, it points out that blocking is possible, suggesting DNS (domain name system) alteration in the short term would be effective until the DNSSEC system is implemented in the coming years, which would render the system less effective.
The sticking block for Ofcom is in the difficulty of providing a framework for any blocking system to be put in place.
"We find that sections 17 and 18 are unlikely to be able to provide for a framework for site blocking which would be effective," states the report.
"We do not believe that it is possible to deliver a framework under the DEA which simultaneously meets the requirements of the copyright owners for a timely implementation of blocks and a flexible approach from service providers to tackling circumvention, with the need to respect the legitimate interests of site operators, service providers and end users."
But, before those who oppose the controversial Digital Economy Act start sending out the party invites, Ofcom concludes: "site blocking could still play an important role in helping to tackle online copyright infringement.
"Further research would be required to identify the most suitable policy framework for implementing such a scheme."