Revelations over the past year about spying techniques at Hewlett Packard, Lidl and, most recently, Deutsche Telekom suggest that some private firms are keeping tabs on their employees from the boardroom to the bathroom. This can be a risky business, and lawyers are increasingly being asked to advise on the sensitive balance between privacy and commercial interests.

Companies already know that letting staff take a walk on the wild side can damage their brand. Car rental firm Hertz dropped Deutsche Bank Securities as underwriter of its stock market debut after one of the bank’s employees sent out emails to a large number of institutional investors. Norwich Union was ordered to pay £450,000 damages after one of its employees wiped out a financial house with a defamatory chain email.