Lawyers have cautiously welcomed recently released figures showing the number of whistleblowers has doubled in the past five years, but they have warned that some spurious claims are being made on the back of the new legislation.

A report from charity Public Concern at Work found that in 1997 and 1998 the numbers of whistleblowing concerns raised on its national helpline were 228 and 230 respectively, in 2001 and 2002 they were 530 and 561 respectively.

A spokesman for Public Concern said: 'Big law firms are now [since the introduction of the Public Disclosure Act 1998] advising their clients to blow the whistle, but legal advice is also preventing firms from gagging their employees.' He said that legal advice often meant that companies - attempting to keep abreast of corporate governance requirements - tempered their internal regulations so they did not appear to be gagging staff .

Julian Hemming, the chairman of the Employment Lawyers Association and a partner at Bristol firm Osborne Clark, said: 'I think a lot of big companies do now have a whistleblowing policy in their portfolio of policies for employees, which is a certain encouragement for people.'

Mr Hemming welcomed the growth in cases, saying that 'people at work should be able to blow the whistle without suffering personal detriment.

The Robert Maxwell case may never have happened in today's environment without someone blowing the whistle'.

But he warned: 'The downside is that there is a slight trend for people to bring claims which take advantage of the fact that such claims can be brought by the employee when there has been less than one year of continuing employment - unlike many other employment claims.'

Sarah James, an employment assistant with Dickinson Dees' Tees Valley office, said: 'This legislation is valuable and important protection for employees, but it can be cynically used which is a sad fact of the current litigious climate.'

She said that Dickinson Dees - which acts for many employers - had seen a number of cases in which employees had tacked whistleblowing public disclosure issues to a general employment claim to take advantage of the fact that there is no cap on compensation, and no upper age limit for applicants.

Jeremy Fleming