Governments around the world are recruiting “cyber-mercenaries” - groups of skilled professionals who target institutions such as banks and energy companies, British politicians have warned.

The Intelligence and Security Committee, which consults with intelligence agencies such as MI5 and MI6, said in its report that, “The threat from cyber attacks is at its highest level ever - and is expected to rise further still with the identification of new actors and more evidence of serious hostile cyber activity.”

The report describes groups of “skilled cyber professionals, undertaking attacks on diverse targets such as financial institutions and energy companies. These groups pose a threat in their own right, but it is the combination of their capability and the objectives of their state backers which makes them of particular concern.”

The Committee also said that professional service firms, such as lawyers and accountants, were increasingly being targeted by cybercriminals.

Britain's Foreign Secretary William Hague described the trend as "worrying" in an FT report, saying that such firms could offer, “a route into a defence company, a high-tech manufacturer. A lot of their data are sitting with their lawyers or their accountants and if they are soft targets, well, then it becomes quite easy to get that data a different way.”

The group’s report said that government agencies were working to convince private companies that they faced a serious threat - and that the financial damage caused by such attacks worked as an “incentive to improve their defences.”

The former Director General of the Security Service was quoted as saying, “One of them... concluded that they had lost at least £800 million as a result of  cyber attacks, and that’s quite a lot of money, even for a major company. But it’s very helpful, because otherwise you are just saying, ‘Well, some information has gone. So what?’”