London: Radical moves to crack down on social media “poison” will be launched this week to try to prevent a repeat of the tragedy of a teenage girl who killed herself after swapping self-harm pictures on a website.

Culture Secretary Maria Miller will challenge social media companies to transform how they police their sites by “pro-actively” removing offensive and dangerous posts as soon as possible.

The measure, to be unveiled at this week’s Cabinet meeting, comes after the mother of 15-year-old Tallulah Wilson, who threw herself in front of a train after swapping self-harm snaps on the photo-sharing website Tumblr, appealed for action to stop the online “poison”.

One online follower of Tallulah had posted a picture of a noose with the message: “Here’s your new necklace, try it on”.

Government sources last night said Miller was determined to do everything possible to prevent a repeat of such a case by putting pressure on social media sites to remove dangerous material far more quickly.

A special conference, to be chaired by Miller, is being planned within the next few weeks. The main companies, Tumblr included, will be invited.

A Government source said: “Some of the behaviour being seen online is deeply disturbing. It would be completely unacceptable to threaten physical violence such as rape or murder during a face-to-face argument so why do people think it is acceptable online?

“Behaviour that is unacceptable and even illegal in the offline world is exactly the same online.”

The social media crackdown will be based on the campaign last year to get the main internet service providers to beef up controls on access by children to online porn. The Government source said: “We put a lot of pressure on the big internet service providers over web porn and it worked.

“All new broadband customers have automatic settings for family-friendly filters to block porn and only the adult account holder can change the setting. We want to do the same sort of thing with social media sites.”

The Mail on Sunday understands the plans were being drawn up before last week’s inquest, when harrowing details of Tallulah’s use of the web became public.

But officials said there was no question the case had “given the whole thing fresh urgency”.

Tallulah, a pupil at the £11,000-a-year (Dh66,682) St Margaret’s School in Hampstead, North-West London, jumped to her death at St Pancras station last October after posting comments such as “I will never be beautiful and skinny” and “I have absolutely no plan for my future”.

Her inquest heard that she had amassed 18,000 followers on Tumblr by swapping the self-harm pictures and had become obsessed with the idea that she was “fat” and “ugly”.

Her mother Sarah said her daughter had been “in the clutches of a toxic digital world where we could no longer reach her”.

She revealed she had contacted Tumblr to get her daughter’s profile shut down but that Tallulah had gone “berserk”.

Wilson called on Tumblr to “do more to protect other vulnerable young people from the insidious aspects of the internet”.

But she also appealed to “big brands to withdraw advertising from sites that continue to host inappropriate self-harming and suicide-promoting blogs to stop this poison spreading”.

A spokesman for Tumblr said last week that “issues of depression and self-harm are extremely challenging, particularly in online environments that encourage self-expression”.

He added that the site had policies to address harmful content and was committed to improving its ability to take action over content relating to self-harm.