A third of firms said they'd lost key financial data because of computer problems or because they'd lost the paper copies.

KashFlow.co.uk, an accounting software development firm, said its research showed many micro businesses and sole traders had only one computer - and if that isn't backed up, just one virus or error could wipe out vital information.

MD Duane Jackson said:

"Despite high-profile campaigns to encourage more businesses to regularly back up data there is obviously still a massive amount to learn and this highlights the very real risk of using a financial software package that is not backed up regularly to a remote location."