One in five businesses run the risk of sensitive information falling into the hands of competitors by failing to remove access rights of former employees, research shows.

Some 23 per cent of companies are leaving corporate networks exposed to the threat of data theft and attacks by former staff by failing to revoke former staff IT access rights for weeks, months and in some cases years after the have left, according to research from Citrix.

The survey of 1,400 IT professionals shows that email access is the business tool most at risk when it came to ex-employees trying to access information remotely.

But confidential company documents, contact databases and administration systems were also at high-risk.

'Firms need to build in rules saying what people can and can not access from the corporate network,' said Thomas Raschke, IDC's programme manager for European security products and strategies.

'Access management is often an overlooked part of the business.'