One in five senior IT staff are "not confident" that none of their old PC's end up in landfills, says Computer Aid International.

Research by the IT charity, which was conducted by Vanson Bourne, revealed just 65 percent of firms surveyed were confident or very confident that all their unwanted IT avoided being sent to landfill, a process which is illegal in the UK as well as being dangerous to the environment and human health,

On average UK firms dispose of 542 computer every year and one third of companies admit to replacing their desktop PCs every three years. Meanwhile, monitors are replaced every five years.

83 percent of senior IT staff say their company is compliant with the WEE Directive that sets collection, recycling and recovery targets for electrical goods. Unfortunately, 13 percent admit to not knowing what the WEE Directive is.

More than a quarter (28 percent) of firms claim to recycle all of their old IT equipment, while 41 percent say they recycle more than half.

Under the WEEE Directive, the preferred method of disposal of old IT equipment is reuse, providing it is working. However, only 14 percent of firms reuse their working equipment and recycle the rest. Of those that don't reuse old IT equipment, 63 percent blame data protection concerns while 24 percent said contractual obligations to a leasing company prevented them from doing so. More than four in five (83 percent) said they would reuse working equipment if factors such as data protection and cost were addressed.

"This research highlights some shocking examples of bad practice in IT disposal among some of the UK's largest companies. It is extremely worrying that many of the UK's largest companies are not able to guarantee that their equipment is not illegally dumped in landfill," said Anja ffrench, director of communications at Computer Aid .

"Companies must use disposal providers that can track exactly where all their equipment is sent to so as to avoid the devastating impact on health and the environment that e-waste can cause."

ffrench also recommended firms put policies in place to ensure more reuse of working equipment.

"Disposing of PCs after four years is a huge waste of resources since most computers will last for at least double this time. Since the vast majority of IT decision makers want to send PCs for reuse, we hope that this research will encourage companies to improve their IT disposal procedures and look for decommissioning providers that guarantee environmentally friendly disposal of non-working equipment and best practice data security while also ensuring that working IT is reused."