New legal guidelines for offensive 
Facebook and Twitter messages

But the question of whether the country needs new laws to deal with offensive posts on social media is a question for Parliament, Mr Starmer said.

Criminal prosecutions against people posting offensive online messages have controversially mushroomed in the past 18 months.

New guidelines are needed because of the potential for a “chilling effect on free speech” as thousands of people could be accused of being criminals every month, Mr Starmer said.

The May 2010 conviction of Paul Chambers for joking on Twitter about blowing up Robin Hood Airport in South Yorkshire is one of most well-known cases in this area. His conviction for sending a “menacing” tweet drew widespread condemnation and was eventually quashed on appeal in the High Court in July.

Mr Starmer now admits that the Crown Prosecution Service (CPS) made the wrong “judgment call” to prosecute the 28-year-old and included his solicitor in discussions over the law.

Now Mr Starmer has set out new interim CPS guidelines designed to raise the threshold against which people should be prosecuted. He said: “In most cases, once you have put the (new) safeguards in place then a prosecution is unlikely to be the appropriate response. To that extent, therefore, it is to make it less likely that these cases will be prosecuted.”

The guidelines are intended to strike the right balance between freedom of expression and upholding criminal law, he said.

Now, social media messages which amount to credible threats of violence; a targeted campaign of harassment; or which breach court orders will be prosecuted.

An example of this is the nine people each ordered to pay the woman raped by footballer Ched Evans £624 for naming her on Twitter or Facebook.

Her naming breached a court order prohibiting the identification of victims of sexual offences. Any similar cases would still be prosecuted robustly.

Aggressive “trolling” would also probably fall under this banner as it could be specifically targeted and constitute harassment or stalking, Mr Starmer said.