A Bill to protect freedom of speech and reform the libel laws is to be introduced into Parliament, it was announced in the Queen's Speech.

It is understood that the Bill is likely to be published on Friday.

The reform, announced in a brief mention in the Queen's Speech, was welcomed by campaigners.

The Libel Reform Campaign - made up of Index on Censorship, English Pen and Sense About Science - which has been calling for legislation to reform the libel law since November 2009, hailed the announcement as a victory.

A spokesman for the campaign said: "The Bill will open the way to ending libel tourism and protecting free expression for journalists, writers, bloggers and scientists around the world.

"However, there is still work to be done and we will carry on campaigning to make sure that the detail in the final Bill will truly deliver reform."

It is understood that the Bill will aim to re-balance the law to ensure that while people who have been defamed are able to protect their reputation, free speech and freedom of expression are not unjustifiably impeded by actual or threatened libel proceedings.

It will also aim to ensure that the threat of a libel action is not used to frustrate robust scientific and academic debate, or to impede responsible investigative journalism, reduce the potential for trivial claims, and address the perception that the English courts are an attractive forum for so-called "libel tourists" who had little connection to this country.

Index on censorship chief executive Kirsty Hughes said: "Finally, the Government is to stop libel tourism so wealthy foreign claimants can no longer use our High Court to silence their critics abroad.

"The 60,000 people who signed the Libel Reform Campaign will be delighted that the Government has announced this reform, though we'll be awaiting the detail."

Sense About Science managing director Tracey Brown said: "We and thousands of others have campaigned to stop the libel laws' bullying and chilling effects on discussions about health, scientific research, consumer safety, history and human rights.

"We are really pleased to see the Government has moved closer to honouring its promise of a fairer law and protection of free speech in today's Queen's Speech. This opens the way to developing a law guided by public interest not powerful interests."

Simon Singh, who became embroiled in a bitter libel battle with the British Chiropractic Association, said he was still being contacted by journalists, scientists and others who were being silenced by libel threats or libel claims.

He added: "The reform promised in the Queen's Speech today is a welcome response to the intolerable effects of the current laws."

Index on Censorship editor Jo Glanville said: "We have now have a chance for libel legislation that's fit for the 21st century.

"The introduction of the single publication rule and greater protection for internet service providers will help to put an end to the chilling effect online."

Justine Roberts, co-founder and chief executive of the Mumsnet website, said: "While the draft Defamation Bill was a very good start, it didn't go far enough to protect freedom of expression, particularly in the online environment.

"Websites and hosts of user-generated comment risk becoming tactical targets for those who wish to clamp down on criticism or investigation of their activities."

Cardiologist Dr Peter Wilmshurst, who was sued by an American medical device company, said: "Patients have suffered because the draconian defamation laws were used to silence doctors with legitimate concerns about medical safety."

Reforms expected to feature in the Defamation Bill will include moves to address concerns about the detrimental effects that current libel law has on freedom of expression, particularly in relation to academic and scientific debate, the work of non-governmental organisations and investigative journalism, and libel tourism.

The Bill is also expected to introduce greater protection for secondary publishers such as booksellers and for website operators in relation to material posted by users of sites which they host - at present, website operators have to remove material when they are told it is defamatory or face the risk of a libel action even though they are not in a position to know whether or not it is defamatory.

The Bill is also expected to end the presumption in favour of jury trial in defamation cases, which currently adds significantly to the cost of cases and the time taken to resolve claims, and stops early resolution of issues such as the actual meaning of words about which the claimant is complaining.

It is also expected to introduce a requirement for a claimant to demonstrate that the published material has caused serious harm - an attempt to stop or discourage trivial claims - and to put the Reynolds defence of responsible journalism on a matter of public interest on to a statutory footing.