The director of public prosecutions is to issue new social media rules on abuse, after Team GB diver Tom Daley received an offensive Twitter message.
Keir Starmer QC said the move would help ensure "decision-making in these difficult cases is clear and consistent".
It comes after a footballer arrested over malicious communications was released without charge.
Mr Starmer said the message had not been "grossly offensive".
Port Talbot Town FC suspended midfielder Daniel Thomas, 28, last month after a homophobic message referring to Daley and fellow Olympic diver Peter Waterfield was sent to Daley's Twitter page.
'Boundaries of free speech'
Mr Starmer - the most senior prosecutor in England and Wales - said the case highlighted the "growing number involving the use of social media".
He said new guidelines were required because "there are likely to be many more - the recent increase in the use of social media has been profound".
Estimates suggest there are 340 million messages posted each day on Twitter - where "banter, jokes and offensive comment are commonplace and often spontaneous", Mr Starmer said.
"Communications intended for a few may reach millions."
Mr Starmer went on: "Social media is a new and emerging phenomenon raising difficult issues of principle, which have to be confronted not only by prosecutors, but also by others including the police, the courts and service providers.
"The fact that offensive remarks may not warrant a full criminal prosecution does not necessarily mean that no action should be taken.
"In my view, the time has come for an informed debate about the boundaries of free speech in an age of social media."
Mr Starmer also announced "a wide public consultation" would take place before final guidelines were published.
Speaking on BBC Radio 4's PM programme, he added that the threshold for prosecution should be high.
"Free speech is fundamental, it's very important it's respected and therefore a criminal prosecution should be reserved for cases that cross a high threshold and the law requires it to be grossly offensive," he said.