This so-called data leakage is a very real concern, according to online security firm Sophos, which found 50% of employees admitted sending an embarrassing or sensitive email from work to the wrong person.

Sophos said this could potentially cause embarrassment, compliance breaches and the loss of business critical information.

A spokesman added:

"Businesses would be wise to check that their e-mail security solutions have the facility to prevent this from happening by identifying when sensitive data or attachments are contained in the message, and if they don't, to consider a more water-tight alternative."