At least 80,000 people in the UK are estimated to pose a sexual threat to children online, the Home Secretary is to reveal.
Sajid Javid will disclose the figure and describe his shock at discovering the scale of the danger posed by paedophiles on the internet.
In a flagship speech, he will outline his "personal mission" to tackle child abuse in all its forms.
Mr Javid is expected to say: "It was when I visited the National Crime Agency's Child Exploitation Online Protection Command that the full horror of the scale and evolving nature of child sexual abuse was really brought home to me.
"One officer I met, who had previously worked in counter-terrorism for over 20 years, told me how in all his years of working he's never been so shocked by the scale of the threat or the determination of the offenders as he is in his current job."
In particular, Mr Javid will describe his horror at discovering the National Crime Agency estimates there are up to 80,000 people in the UK who "present some kind of sexual threat" to children online.
Operational experts say that is a conservative estimate.
Other new statistics reveal referrals of child abuse images to the NCA have surged by 700% in the last five years.
Images are getting more graphic, with abuse of babies and children under 10 more regularly documented, the Home Office said.
The department also warned that live-streaming of abuse is an increasing trend due to faster internet speeds, smartphone technology and the growing ease of money transfers across borders.
Separate figures indicate that police in England and Wales recorded around 23 child sexual offences involving the internet every day in 2017/18 - up from a rate of around 15 a day in the previous 12 months.
The scale of the offending has prompted demands for internet giants to take more action to stop access to sexual abuse images and videos.
National Police Chiefs' Council lead for child protection Simon Bailey said:"The police response
to tackling child abuse online has been robust, but there is a growing need to pursue offenders who pose the most harm to children and are using sophisticated technology to evade detection.
"Technology plays a significant part in all online investigations and there is an expectation that technology companies acknowledge their social responsibility in preventing and designing out this type of offending from their platforms.
"Only by working collaboratively with technology companies and law enforcement partners will we be able to minimise the risk posed to children online by predatory offenders."
There have also been calls for offenders who download indecent images of children to get tougher sentences.
Last month, Solicitor General Robert Buckland said the use of the internet to download or share images of child abuse is "as insidious a crime as direct sexual assault".
In his speech, Mr Javid is expected to commit to prioritising urgent work to crack down on online child sexual abuse.
This will build on previous Government measures, including a £600,000 investment in a project that trawls the web to identify pages with suspected abuse content.
The Internet Watch Foundation (IWF), which assesses and removes online child abuse material, said it fully supports Mr Javid in his warning.
Susie Hargreaves, chief executive of the IWF, said it "recognises the evolving threat of child sexual abuse online and the problems highlighted by the Home Secretary, in particular live streaming, encryption and grooming".
She added: "Sadly, our most recent annual report showed that the severity of the images we identified were up and it appeared that offenders were becoming more sophisticated in their crime."
Ms Hargreaves added that the UK "remains one of the most hostile places in the world to host this disturbing material".
Javed Khan, chief executive of children's charity Barnardo's, said: "We welcome Sajid Javid's commitment to ramp up the Government's efforts to tackle online child sexual abuse.
"The Government must now deliver its promise to make the UK the safest place to be online by forcing online companies to ensure effective safeguards are in place to help better protect children.
"Any delay to acting now could put a generation of children in danger online."
Copyright (c) Press Association Ltd. 2018, All Rights Reserved. Picture (c) Joe Giddens / PA Wire.