The Libel Reform Campaign said the Defamation Act 2013, which came into force on 1 January 2014, "is making a positive impact".
The Act introduced a new requirement that publication of a statement caused, or is likely to cause, serious harm to the reputation of the claimant before it can be found to be defamatory. In the case of "bodies trading for profit", serious harm is harm that caused, or is likely to cause, serious financial loss.
The Libel Reform Campaign said that recent court rulings on the meaning of 'serious harm' under the Act "show that trivial claims are being discouraged".
"Judges have affirmed the politicians’ intent that claimants have to prove they had been harmed or prove that harm will result in the future," the Libel Reform Campaign said. "This is not an insurmountable hurdle for those with a genuine case, but lawyers tell us that it has resulted in fewer trivial claims being launched. We campaigned hard for this measure and we’re delighted it is making a difference."
The Libel Reform Campaign said that the defamation reforms had also helped to discourage "libel tourism", where libel claims concerning people and publications based overseas are brought before the UK courts.
The group outlined plans to lobby for reforms of defamation laws in Scotland and Northern Ireland in 2016.