Fines of £10,000 for social media bosses who don't remove illegal knife adverts are being considered by the government.
The proposals are part of attempts by Labour to fulfil their promise to halve knife crime levels in the next decade.
The Home Office wants to introduce the measures to stop the "unacceptable use of social media and online marketplaces to market illegal weapons and glorify violence" and ensure content is quickly removed.
Under the plans, police would be empowered to issue warnings to senior officials at online companies and demand specific adverts and content be removed - potentially within two days.
A second notice could then be given if action is not taken - with senior executives "personally liable" for a "significant fine" if nothing is done.
While the exact scale of the financial penalty has not been confirmed, a consultation suggested £10,000 for the worst offenders, according to the PA news agency.
Sir Keir Starmer previously spoke of his desire to make buying knives online harder.
In September, he hosted a meeting of a new anti-knife crime coalition including actor Idris Elba and bereaved families, among others.
Elba told the meeting: "Talk is good, but action is important."
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As well as reducing the sale of knives online, the government also wants to change the law around ninja swords.
Work is currently ongoing to decide a definition of the weapons.
It comes on the back of campaigning by Pooja Kanda, the mother of 16-year-old Ronan Kanda.
Ronan was killed in Wolverhampton by two 17-year-olds in 2022, who used a weapon purchased online under an alias and collected from a Post Office.
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Home Secretary Yvette Cooper said perpetrators "must face the full force of the law" as she announced the "tough new sanctions", adding: "The epidemic of knife crime that has grown over the last decade is devastating families and communities right across the country.
"That's why this government has set out an unprecedented mission to halve knife crime over the next decade and today we're taking determined action to get lethal blades off Britain's streets."
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Commander Stephen Clayman, who leads the National Police Chiefs' Council's work on knife crime and is also heading a review of online sales of the weapons for the Home Office, said: "For far too long, deadly weapons have been far too easily accessible online, with content promoting their use for protection and combat rife on many platforms and seemingly little being done to remove it.
"We welcome the chance to take part in the consultation and explore the most effective means of achieving this, including using the findings of the ongoing online sales review."