The encouragement of self-harm volition beryllium criminalised successful an update to the Online Safety Bill, the authorities has said.
Content that encourages idiosyncratic to physically harm volition beryllium targeted successful a caller offence, making it illegal.
The authorities said the changes had been influenced by the lawsuit of Molly Russell - the 14-year-old who ended her beingness successful November 2017.
Culture Secretary Michelle Donelan said she was strengthening the measure "to marque definite these vile acts are stamped out".
"I americium determined that the abhorrent trolls encouraging the young and susceptible to self-harm are brought to justice," she said.
Molly Russell, from Harrow successful north-west London, took her ain beingness aft viewing termination and self-harm content connected Instagram and Pinterest.
Her begetter has antecedently criticised delays to the Online Safety Bill and called for online platforms to halt self-regulating their content.
At the inquest, the coroner concluded the schoolgirl died portion suffering from the "negative effects of online content".
In October, Coroner Andrew Walker wrote to societal media firms and the government to telephone for changes including abstracted platforms for adults and children.
Ms Donelan said societal media firms could nary longer beryllium "silent bystanders" and they would look fines for "allowing this abusive and destructive behaviour to continue".
She said the update to the Online Safety Bill would make a caller offence, bringing self-harm contented successful enactment with communications that promote termination - which is already illegal.
The amendment would mean societal media platforms would beryllium required to region self-harm contented and immoderate idiosyncratic recovered to person specified contented would look persecution.
More details astir the maximum punishment would beryllium published successful owed course, the authorities said.
The NSPCC's Richard Collard said it was "good news" the authorities was recognising the dangers of children being exposed to online contented promoting self-harm.
But helium said a "culture of compliance and accountability" from exertion firms that person allowed this benignant of contented "to dispersed similar chaotic fire" was needed.
The Online Safety Bill is owed to instrumentality to Parliament successful aboriginal December, pursuing a fig of delays.
The integer section said it could not accidental erstwhile the amendments would beryllium tabled.
Earlier this week the authorities announced different caller offences being added to the measure that would ace down connected the sharing of intimate images without consent.
Representative's from some Pinterest and Meta, Instagram's genitor company, gave grounds during Molly Russell's inquest.
Meta enforcement Elizabeth Lagone said she believed posts seen by Molly, which her household accidental "encourage" suicide, were safe, but the steadfast agreed that regularisation was needed.
Judson Hoffman of Pinterest told the inquest the tract was "not safe" erstwhile the schoolhouse miss was utilizing it. The institution said it was "committed" to making ongoing improvements to assistance guarantee the level is "safe for everyone".
Deputy Prime Minister and Justice Secretary Dominic Raab said "lives and families" had been destroyed by "those who promote susceptible net users to self-harm".
"Our changes volition guarantee the afloat unit of the instrumentality applies to those callous and reckless individuals who effort to manipulate the susceptible online successful this way," Mr Raab said.