Internet trolls who create derogatory hashtags or post humiliating photoshopped images online could face prosecution under new legal guidelines.

Social media is to be more stringently policed after the Crown Prosecution Service issued rules on offences for which online users can face criminal charges.

Inciting people to harass others online, known as virtual mobbing, is among the offences included in the guidance published on Monday.

It is hoped the updated information will help police to determine whether to press charges against someone for their behaviour on social media.

It comes after a major report this year found one in four teenagers suffered abuse online because of their gender, sexual orientation, race, religion, disability or transgender identity.

Cases of sexting that involve underage children should not be pursued for prosecution if the images are shared consensually between two children of a similar age in a relationship, the CPS said.

But it added that if such cases involved "exploitation, grooming or bullying", it may be appropriate to attempt to prosecute those responsible.

Creating a hashtag to encourage an online harassment campaign, or pushing for retweets of a "grossly offensive message" are given as examples of unacceptable cyber behaviour.

Other examples of outlawed practices set out in the guidance include publishing an individual's home address or bank details on the internet, dubbed doxxing.

Baiting - when someone is humiliated online by being branded sexually promiscuous - is also mentioned in the guidance, as is posting "disturbing or sinister" photoshopped images of someone on a social media site.

Prosecutors acknowledged, however, that many photoshopped images were "humorous and inoffensive".

The CPS also announced the launch of a hate crime consultation, issuing a series of public policy statements centred on combating crimes against disabled people, as well as racial, religious, homophobic and transphobic hate crime.

The consultation will be launched on Monday and will last for 13 weeks.

The updated social media guidance also covers hate crime, as well as new areas on violence against women and girls, and vulnerable victims.

Director of Public Prosecutions Alison Saunders said: "Social media can be used to educate, entertain and enlighten, but there are also people who use it to bully, intimidate and harass.

"Ignorance is not a defence and perceived anonymity is not an escape. Those who commit these acts, or encourage others to do the same, can and will be prosecuted."