Tens of thousands of Britons' identities are up for sale on the Dark Web, it has been reported.
The details of more than 600,000 customers were stolen from companies in the UK last year, according to the Financial Times.
They have since been put up for auction on what is described as the internet black market, which cannot be accessed with ordinary search engines such as Google and instead relies on the use of a covert internet browser called TOR.
The average cost for a Briton's personal details is 30 dollars (£19.60), a Whitehall security official told the paper.
Profiles have been stolen from the Government's own computer systems, the paper reported. It claimed these hold enough detail to take control of a person's digital identity.
A Government spokesman told the Financial Times: "We are looking carefully at the level of regulation.
"Every company board should be fully aware of the risk from cyber attack, and be confident that the company has proper security in place."
There were almost one million new cyber threats released online every day last year, according to a report by anti-virus and web security experts Symantec released in April.
Phone and broadband provider TalkTalk was targeted in a cyber attack a week ago, in which it said bank account numbers and sort codes, like those printed on a cheque, may have been accessed.
The company has said criminals would need more information to enable them to take money from a customer's bank account, adding: "Even then, the chances are very small indeed."
A 15-year-old boy arrested in Co Antrim as part of a joint investigation, which involves the Met's cyber crime unit, has been released on bail until a date in November.
Additional reporting by the Press Association
