Less than 25% of old computers sold or given away by companies have had data removed from them, raising concerns about personal information security.
Legislation requires companies to minimise electrical landfill
Of 350 companies surveyed for Remploy e-cycle, over 75% had sold or given away computers but only 23% cleansed the data to make it unrecoverable.
Those surveyed included financial firms which hold sensitive data on customers.
The survey was held ahead of the introduction of a directive encouraging companies to recycle IT equipment.
The Waste Electrical and Electronic Equipment Directive sets out to minimise the amount of such equipment going to landfill.
Thirty-eight per cent of respondents reformatted the drives before they got rid of them and 22% overwrote them once, the survey showed.
Such methods would still allow the data to be recovered, said Noel Harasyn, Remploy e-cycle's business manager.
"Quite frankly, this is deeply disturbing.
"It is laudable that companies are already making redundant equipment available for re-use but in the overwhelming majority of cases, they are not rendering the data on hard drives unrecoverable," he said.
Remploy recycles white goods and computers.
Over 16% of the companies interviewed were from the financial services sector, often holding highly sensitive personal or corporate information.
However, only 12.5% of those companies destroyed data to the required standard.
Once the issue of data destruction was explained during the survey, 23% of companies "admitted to having no idea as to how they would make them safe".
However, the survey did reveal that the Department of Trade and Industry's efforts to raise awareness of the WEEE directive had worked.
Just over 90% of companies interviewed said they were aware of its arrival - in early 2008.
However, 16.5% had no systems in place to ensure and monitor compliance.
Just under 60% of companies said they would be making end-of-life IT equipment available for re-use and that many of them would encourage re-use and refurbishment as part of their Corporate Social Responsibility programmes.
Although the majority of companies said they send end-of-life electrical and IT equipment to be recycled, 29% scrapped electrical equipment, with most probably going straight to landfill, and 10% send their old IT equipment direct to landfill, the survey showed.
Under the directive, producers of electrical and electronic goods will have to arrange for and finance collection of their products at their end-of-life.
The aim is to conserve landfill and to support more sustainable development by boosting recycling.