Police are investigating the disturbing incident amid concerns that the images – apparently taken in a public area of the concert site and now widely circulating on the internet – amount to child pornography because she is under 18.

And dozens of internet commenters have been accused of sexism for mocking the girl and seeking to reveal her identity – while praising her sexual partner as a ‘hero’ and a ‘legend’.

Campaigners have warned that the sharing of explicit pictures is a ‘growing problem’ which it is almost impossible to prevent due to the fast-moving nature of social networking.

Twitter row: There is no suggestion that the man who she was photographed performing a sex act on at Slane Castle, in Ireland, assaulted her

The photograph of the schoolgirl performing oral sex on a grinning man wearing a green hat was taken in the grounds of Slane Castle on Saturday evening.

She was also pictured kissing the same man while he sexually touched her, and giving oral sex to a different man on the same night.

American rapper Eminem was performing to a crowd of 80,000, with police making 63 arrests during the event.

Many of the Twitter and Instagram accounts which shared the pictures of the girl have been shut down, as has a ‘slut-shaming’ Facebook page which made fun of the incident.

But the concert achieved web notoriety the next day when the explicit pictures were widely circulated.

Many internet users were quick to condemn her behaviour – Bridget Moynihan tweeted that the girl ‘has only herself to blame, out in the open surrounded by people with camera phones. What did she expect.’

Users of web forums revealed the identity of the teenager, a secondary school student from the west of Ireland.

Others shared images mocking the girl and implying that she was overly sexually promiscuous.

Encounter: The teenager was pictured kissing the man in a green hat at the same festival

It was reported that the person originally responsible for posting the pictures online was a man from Belfast.

After the girl’s rise to fame, she was apparently left extremely distressed and embarrassed.

She is currently in hospital, and is believed to have been sedated.

‘This is a very sensitive matter and the girl’s family are distraught,’ a source told the Irish Sun. ‘This is so out of character for her. She’s currently very emotional and confused about the whole thing.’

Police are currently investigating the matter, and are looking into who shared the original photos and whether they constitute child pornography.

A police spokesman said: ‘Gardai are aware of the incident and are inquiring into the matter. Gardai have spoken to the female involved and it would be inappropriate for us to comment any further.’

The concerts at Slane Castle, which take place every year and are considered among the highlights of the Irish musical calendar, are organised by Lord Conyngham, who lives at the castle and is known as the ‘rock ‘n’ roll aristocrat’, and promoted by MDC Productions.

Venue: The photograph was taken in the grounds of Slane Castle, in County Meath in Ireland

Social networks have asked users to report the images as quickly as possible so that they can be spotted and removed by site moderators, who have been instructed to remain extra-vigilant in looking out for the images from Slane Castle.

A Twitter spokesman said: ‘Protecting people’s experience on Twitter is very important and we have a clear set of rules that outline what is and isn’t acceptable behaviour on the platform.

‘If people come across content that may violate our policies, we encourage them to report it so we can quickly follow up, rather than tweet or retweet images and links.’

A spokesman for Facebook said: ‘At Facebook we take safety incredibly seriously, and have worked hard for years to develop clear rules and powerful reporting tools that enable people to easily report things that make them uncomfortable. We have built a large and highly trained team of safety experts who review these reports and take action, including escalating serious cases to the police.

‘Unfortunately, there will always be a tiny number of malicious people who are intent on harming others, online and offline. It is difficult to prevent this minority from behaving in this way – but once they do we will work hard to remove them from Facebook and make sure they are brought to justice.’

Cyber-bullying campaigners warned that this type of incident is increasingly common, especially as web users aim to damage the reputation of people they know by spreading photographs of them in compromising positions.

Gig: The incident took place on Saturday during a concert by American rapper Eminem

‘This particular problem is a big one, and it is growing,’ said Scott Freeman, founder of charity Cybersmile. ‘With the power of the internet, this is one example of how its immediate reach can cause huge destruction.

‘It’s almost impossible to protect against it, because anyone can take a picture of anyone and share it.’

He said that websites and internet service providers have a duty to crack down on this type of harmful content, adding: ‘If anyone finds themselves in this situation, they need to contact ISPs and website moderators to get the content removed.’

Last night Clíona Saidléar, policy and communications director with Rape Crisis Network Ireland, said the people who filmed the incident and shared it should be ashamed.

Ian Power, communications manager with youth group Spunout, said that the pictures should never have been posted online. ‘This is content which should never have been recorded, let alone placed on the internet,’ he told the Irish Daily Mail.

‘Everyone has made mistakes in their lives, but not everyone has had it so horrifically documented in such a mortifying way. The conversation online has been overwhelming misogynistic also. Some people seem to be regarding this as funny, or banter, when it is not.’

Jackie O’Callaghan of the National Parents’ Council said that the incident has left many parents worried about their children when attending concerts such as the one at Slane. ‘As a parent, hearing about this did make me worry, of course, and it would worry other parents,’ she said.

Victim: Hannah Smith killed herself this month after receiving abuse from trolls on social network Ask.fm

Despite the widespread condemnation of the girl, very little criticism has been made of the unidentified men featured in the photographs.

Twitter user Conor McCullagh wrote: ‘What about the hero who was with [the girl], now he deserves a medal.’

However, others took to the internet to criticise the apparent double standards.

@zintendo wrote on Twitter: ‘Cute that everyone is talking about [the girl], nobody is judging the guy. #yourmisogynyisshowing’.

Journalist Sarah Ditum wrote on the New Statesman website that the man was considered just ‘a bystander’ while ‘people tried to use the pictures to shame, trash and demolish a young woman’.

The alleged misogyny comes in the wake of complaints from prominent women, including MPs, that they have been the subject of vile threats delivered via Twitter by anonymous trolls.

A British teenager, Hannah Smith, killed herself earlier this month after being mercilessly bullied by trolls on social network Ask.fm, leading to calls for greater action over online abuse.