UK provider TalkTalk is facing a compensation bill that could be worth millions after customer details were stolen in a high-profile cyber attack.
Reports have already suggested the total amount lost in revenue and compensation could be as high as £75 million, with one expert likening it to "Great Train Robbery of the 21st century".
TalkTalk revealed the data hack, which was allegedly carried out by a Russian-based Islamist group, put up to four million current and former customers’ details at risk, although it has now claimed the attack may not be as bad as first feared.
But Mr Culley, a former Metropolitan Police detective and a security consultant, said TalkTalk is now likely to face a substantial compensation bill.
He told the Sunday Telegraph: “This is one of the biggest crimes ever. It is the Great Train Robbery of the 21st century.
“There is a potentially huge liability for TalkTalk as a result of this."
TalkTalk's chief executive Dido Harding told the Daily Mirror that cyber experts from BAE Systems have already been drafted in to establish the extent of the breach, sifting through around one billion points of data.
She added that any stolen information was not enough for hackers to raid bank accounts, before stating that the future of the company would be dependent on restoring trust with its customers.
"The future depends on what we do over the next few weeks," she said.
"If we look after our customers through this really difficult time when we have all been victims of a crime together then I hope they will forgive us.
“If we don’t look after them properly, they won’t, so it is within our gift to do that.”
Meanwhile, reports have also suggested that TalkTalk is still charging customers an ‘early leavers fee’ of up to £360 for trying to cancel their contracts and move to another provider.
The company has said it is to hold customers to their deals until a police investigation and an internal enquiry had been completed.