Alternative blocking measures that tackle illegal file-sharing will be explored instead, it said.
Provisions within sections 17 and 18 of the Digital Economy Act (DEA) allow the Culture Secretary to draw up new regulations that would see courts decide whether to force ISPs to block access to pirated copyright works, but for the moment the Government has decided not to write the new laws.
"Ofcom concludes that the blocking of infringing sites could potentially play a role in tackling online copyright infringement, but that the approach set out in the DEA is unlikely to be effective because of the slow speed that would be expected from a full court process," a Government policy statement (10-page / 160KB PDF) on the implementation of the DEA said.
"This would provide site operators with the opportunity to change the location of the site long before any injunction could come into force. The Government will not bring forward regulations on site blocking under the DEA, at this time," the statement said.
In its report Ofcom had said the new laws would not be sufficiently predictable, low cost and fast to implement for rights holders to benefit from.
"We do not think that sections 17 and 18 of the Act would meet the requirements of the copyright owners," Ofcom's report (56-page / 1.99MB PDF) into website blocking said.
"Specifically, we do not think that using the DEA would sufficiently speed up the process of securing a blocking injunction, when compared to using section 97A of the Copyright Designs and Patents Act, which already provides a route to securing blocking injunctions. As a consequence we are sceptical as to whether copyright owners would make sufficient use of any new process," the report said.
Last week the Motion Picture Association (MPA) won a landmark High Court ruling against the UK's biggest internet service provider (ISP) BT. The MPA successfully argued that BT should block its customers' access to a website that provides links to pirated films.
Six major film studios - including Warner Brothers, Disney and Fox – had requested the action.
The High Court made its ruling under section 97A of the Copyright Designs and Patents Act. That section gives UK courts the power to grant an injunction against an ISP if it had 'actual knowledge' that someone had used its service to infringe copyright.
The Act does not specify what purpose an injunction must serve. Section 97A implements the requirements of the EU Copyright Directive which states that countries must ensure that copyright holders have the right to apply for injunctions against intermediaries, such as ISPs, whose services are used to infringe copyright.
The case is the first time that an ISP has been ordered to block access to such a site under UK copyright laws.
In its report Ofcom said that effective website blocking measures could be obtained using existing technical measures.
"If the Government was minded to pursue the objective of implementing a site blocking scheme, we would recommend that further research be undertaken to identify and evaluate alternative legal frameworks which would be more suitable," Ofcom said.
"In particular, we would suggest any research considers how to best harness the potential value of complementary approaches, such as search engine de-listing, measures to constrain advertising and subscription revenue sources, as well as notice and take down approaches. Site blocking could potentially be more effective if it was supported by the appropriate use of such measures," it said.
The technical measure preferred by Ofcom for blocking access to illegal content was re-directing users away from illegal content using alterations to the domain name system (DNS).
"We consider DNS blocking to be the technique which could be implemented with least delay," Ofcom said in its report.
"While it carries a risk of over blocking, since it blocks at the level of the domain (blocking all websites in the blocked domain, when only one may have been infringing), it would be quick to implement, as existing systems could be easily adapted, and would appear to require only fairly modest incremental investment for service providers," it said.
Operators of websites need to be better identifiable in order for blocking measures to work, Ofcom said. It also said ISPs could take days to implement blocking measures under current systems and that automating the process could be a potential solution to speeding up the implementation of measures.
ISPs must also be protected from being legally responsible for "over-blocking" access when implementing a court injunction, whilst the risk of blocking access to legitimate content must also be reduced in order for existing measures to become more useful, Ofcom said.
The Government said it is already working with industry and law enforcement bodies to find better ways to combat websites that infringe copyright.
"We are already exploring measures which target the revenue streams of websites dedicated to infringing copyright, such as banning advertising on these sites and withdrawing payment facilities," the Government's statement said.
"We also want to work with search engines to investigate how it could be ensured that unlawful sites do not appear higher up in search rankings than legitimate sources of digital content, without distorting legitimate online business or harming fair competition," it said.
The Government also announced the implementation of the initial obligations of the DEA in its policy report. Separate coverage of this story will be available on OUT-LAW later.