Unsuspecting young girls are being abused at organised “sex parties” advertised on social media, a charity worker in Barking and Dagenham has warned.

At so-called uck parties, also known as line ups, girls as young as 13 are plied with alcohol and drugs and then expected to perform sex acts on multiple men, or possibly face violence.

Some victims think they are attending an ordinary party and have no idea what awaits them.

The parties are “happening in London and are one of many ways young people are exploited”, one charity said.

Serrina Lobban, who leads Barnardo’s Stop It Before It Starts in Barking and Dagenham, said footage from the events is then often used to “blackmail or shame” girls online.

She said “Young people may think they are being invited to a normal party but when they get there they find it is something different.

“’Uck’ is a reference to oral sex and girls will find men standing in a line. It can be older men or it can be peer on peer.”

Ms Lobban said some of the teenagers her team work with may have attended these parties, and almost all have seen explicit videos of young people shared on “bait out pages” online.

“We have seen children going on ‘bait out’ pages, where the people running them will say they are ‘exposing hos’ in a certain borough,” she said.

“They will shame these girls who may have been to an uck party. Victim-blaming is normalised.

“But boys can also be the victims. They will go to these parties and find they are expected to engage in sexual activity.

“People are becoming more aware and we have seen some girls have had the resilience to leave when they realise what is going on. But it can be difficult when you don’t always know how the [organiser] might react.”

While uck parties or line-ups are not explicitly linked to London gangs, it is believed that many of young people attending will be a member of or know someone in a gang.

This means victims are often wary of going to the police, said Ms Lobban.

“If they’ve been invited to a party or have seen a video from one they do not share it with the police,” she said.

“They don’t see the police as a source of protection.”