A number of Liberal Democrats have raised concerns over an amendment to a clause in the Digital Economy Bill that would see websites carrying copyright infringing material blocked.

The amendment to Clause 17, which was passed by the House of Lords this week, is designed to "prevent access to specified online locations for the prevention of online copyright infringement".

According to Lord Clement-Jones, the amended clause now offers a "more proportionate, specific and appropriate" way to deal with internet piracy and will hopefully quash fears that web users accused of illegally downloading would be disconnected from the net under the 'three strikes' rule, which is also set-out in the Digital Economy Bill.

"I believe this is going to send a powerful message to our creative industries that we value what they do, that we want to protect what they do, that we do not believe in censoring the internet but we are responding to genuine concerns," he said.

However, the amendment raised a number of concerns that websites would shut down, based on the threat of legal action.

This has prompted 25 Liberal Democrat MPs to write an open letter saying the blocking website is "both draconian and unworkable" and calling for a re-think of the policy.

"Using the courts runs the same risk as the libel laws, of empowering the rich and well-connected to close down comment from those who may have right on their side, but cannot afford to contest cases."

The MPs added the legislation would have a detrimental effect on free speech in a free society.

The letter comes as senior industry sources told The Guardian they expect the Digital Economy Bill to be passed before Parliament is dissolved in April ahead of the anticipated general election.

See also: Digital Economy Bill could wipe out free Wi-Fi