The Director of Public Prosecutions appeared on talkRADIO this morning to map out her team's new plans to tackle hate crime.
Alison Saunders told Paul Ross people can have "distasteful" opinions, but the Crown Prosecution Service (CPS) will get involved if it becomes "grossly offensive."
The CPS launched a crackdown on both online and offline hate crime on Sunday, by releasing a set of new guidelines for prosecutors to follow.
The changes could be the trigger for a dramatic increase in the number of prosecutions for posting offensive content on social media.
Saunders told Paul Ross about the CPS's new social media campaign, and insisted it wouldn't get in the way of the right to free speech.
She said: "I think free speech is important. Our guidance must make clear that prosecutors will need to balance the right to [use] it.
"That means people can hold and vocalise distasteful, insulting behaviour, but when it crosses the line into grossly offensive or threatening and abusive, that is a line when it’s crossed, we will prosecute.
"Free speech doesn’t mean you can threaten people or post grossly offensive messages online, that’s not what people can do."