The National Crime Agency and the head of Counter Terrorism Policing in the UK have both welcomed the Online Harms Paper, which was published for consultation on Monday, 8 April.
The White Paper — which was leaked last week — proposes directly regulating social media companies for the first time, with senior executives facing fines if they fail to block damaging content such as terrorist propaganda or live streaming of child abuse.
The regulations would create a statutory "duty of care" for social media companies such as Facebook and Twitter to protect young people who use their sites.
The rules would be overseen by an independent regulator, funded by a levy on internet companies.
"Voluntary actions from industry to tackle online harms have not been applied consistently or gone far enough," said Media Secretary Jeremy Wright.
"Internet companies have been slow to acknowledge their social responsibility and although they are now doing more to prevent harmful material such as child abuse imagery or terrorist propaganda, I'm delighted to see the government move decisively to make the internet a safer place for us all," said the National Police Chiefs' Council lead for public protection, Chief Constable Simon Bailey.
"These new regulations will assist policing in our battle to keep young people and vulnerable adults safe, by allowing us to focus our resources on pursuing offenders in the UK and preventing the proliferation of material that harms our society," said Mr Bailey.
"This White Paper is a welcome announcement for those of us working to keep the public safe from the unprecedented terrorist threat," said the Metropolitan Police's Head of Counter Terrorism Policing, Assistant Commissioner Neil Basu.
He said the Counter Terrorism Internet Referral Unit had successfully removed more than 310,000 pieces of extremist material since 2010 but it was "a drop in the ocean" considering how much terrorist propaganda is still available online.
"Every single terrorist atrocity that took place in the UK during 2017 included some element of online radicalisation or attack-planning, and we have been arguing for years that internet companies must take greater responsibility for the threat posed by material they host on their platforms," said Mr Basu.
National Crime Agency director Rob Jones also welcomed the White Paper.
"The fantastic opportunity the internet gives us should not be exploited by cynical and predatory sex offenders. The NCA is seeing an increase in the scale and severity of child sex abuse," said Mr Jones.
He said there were 110,000 global reports of online child sex abuse in 2004 but by 2018 that had risen to 18.4 million.
"Industry must block abuse images upon detection and prevent online grooming, it must work with us to stop live-streaming of child abuse," Mr Jones said.