A number of building firms embroiled in a row over the sale of workers' data have denied taking part in unlawful activities.

The Information Commissioners Office (ICO) said last week that The Consulting Association, which collates information of employees of the construction industry, had sold over 3,000 workers' personal data - including employment history and trade union activity - to building firms without their consent.

According to the watchdog, the 'secret' system has been running for 15 years, allowing building firms, including Taylor Woodrow and Balfour Beatty, to illegally vet potential employees. It said it was considering legal action against the firms that purchased the data for The Consulting Association.

The companies paid an annual fee of £3,000 and then £2.20 for details on each potential employee, the ICO said.

PC security advice

Broadband speed tester

However, Balfour Beatty said it does not condone 'blacklisting'. "We have taken steps to ensure that none of our companies use the services of the Consulting Association," it added.

A spokesman for Amec added: "Amec does not operate a policy of 'blacklisting' individuals and the senior management of the company would not condone such a policy".

See also: 6m people's data posted online in Chile