The number of people out of work and on long-term sickness benefits because of stress and mental disorders has soared since 1997, say the Conservatives.

The figures, revealed yesterday in answers to parliamentary questions, show almost 1.1m people were claiming incapacity benefit last year who said they were unable to take a job because of problems with mental health, up from 730,000 in 1997.

The number of claimants suffering from severe stress had trebled to 49,000 while those who had endured episodes of depression had almost doubled to 501,000. Those suffering from alcohol or drug-related problems almost doubled to 137,000.

The government has put plans to cut the number on incapacity benefits from 2.6m to 1.6m within a decade at the heart of a drive on welfare reform. Under the welfare reform bill before parliament, claimants could receive a reduced benefit if they failed to turn up for Jobcentre interviews or take part in rehabilitation or training schemes.

But David Ruffley , shadow welfare minister, said the mentally ill could suffer if mental health services continued to be cut to help meet cash pressures elsewhere in the National Health Service.

"Ministers should not use this as an excuse to penalise people on benefit with mental health problems who have been let down by Labour's NHS funding crisis," Mr Ruffley said.

The rising proportion of claimants who suffer from mental disorders is a reflection of a service-dominated economy. Many male manual workers made redundant from heavy industries in the 1980s only to spend the rest of their working lives on long-term sickness benefits have reached pension age.