Hackers say they have stolen the pictures, names and addresses of around 8,000 children from the Kido nursery chain.
A group of cyber criminals says it is using the highly sensitive information to demand a ransom from the company, which has 18 sites in and around London, with more in the US and India.
The criminals say they also have information about the children’s parents and carers as well as safeguarding notes.
They claim to have contacted some parents by phone as part of their extortion tactics.
The BBC has contacted Kido for comment. It is yet to confirm the hackers’ claims.
But an employee at one of the nurseries confirmed they have been notified of a data breach.
Cyber-security firm Check Point described the targeting of nurseries as “an absolute new low”.
One of its experts Graeme Stuart said: “To deliberately put children and schools in the firing line, is indefensible. Frankly, it is appalling.”
The hacking group responsible for the claims appears to be relatively new and calls itself Radiant.
The cyber criminals contacted the BBC about the hack and have subsequently posted details of it to their darknet website.
It has published a sample of data there including pictures and profiles of 10 children from the stolen data set.
It has been published as part of their attempt to extort money from the nursery chain, which has its 18 nurseries mostly in the London area.
Police advise not to pay ransoms as it further fuels the cyber-crime ecosystem.
When asked by BBC News if they felt bad about extorting a nursery using the children’s data, the criminals said they “weren’t asking for an enormous amount” and they “deserve some compensation for our pentest.”
A “pentest” – or penetration test – is the term for when ethical hackers are hired to assess the security of an organisation in a controlled and professional way.
These hackers however attacked the nursery chain without their permission.
“Of course” it’s about money, they admitted to the BBC.
The hack is the latest in a series of high-profile cyber-attacks, which has seen production grind to a halt at Jaguar Land Rover, and caused massive disruption to M&S and the Co-op.
Additional reporting by Graham Fraser, Technology reporter
