Websites will be legally obliged to provide victims with the identity of people who post abusive and defamatory online messages about them under plans by the Government.
Major reforms of the libel laws will also see internet service providers given greater protection from being sued if they help to identify so-called internet trolls.
Would-be claimants will have to show they have suffered serious harm to their reputations, or are likely to do so, before they can take a defamation case forward.
The Defamation Bill will be debated in the Commons later today.
Justice Secretary Ken Clarke said: "As the law stands, individuals can be the subject of scurrilous rumour and allegation on the web with little meaningful remedy against the person responsible.
"Website operators are in principle liable as publishers for everything that appears on their sites, even though the content is often determined by users.
"But most operators are not in a position to know whether the material posted is defamatory or not and very often - faced with a complaint - they will immediately remove material.
"Our proposed approach will mean that website operators have a defence against libel as long as they comply with a procedure to help identify the authors of allegedly defamatory material."
He added: "The Government wants a libel regime for the internet that makes it possible for people to protect their reputations effectively but also ensures that information online can't be easily censored by casual threats of litigation against website operators.
"It will be very important to ensure that these measures do not inadvertently expose genuine whistleblowers, and we are committed to getting the detail right to minimise this risk."
It comes after Frank Zimmerman narrowly escaped jail when a judge suspended a 26-week prison sentence for two years after he sent a threatening email to Conservative MP Louise Mensch.
Zimmerman, 60, who posed as a member of online hacking group Anonymous, sent the mother-of-three an email telling her that she would have to choose which one of her children would die.
The Bill will also replace the common law defences of justification and honest comment with new statutory defences of truth and honest opinion.
The so-called Reynolds defence of responsible journalism published in the public interest also gets statutory recognition, as responsible publication on a matter of public interest.