Up to half of all doctors working in hospitals and general practice suffer 'psychological disturbance' which affects patient care, John Wyn Owen, secretary of the Nuffield Trust told a conference workshop.
Of those doctors reporting stress affecting patient care, one in 10 admitted 'serious clinical mistakes', including patient deaths.
'The last government wouldn't give leadership on this issue,' said Mr Wyn Owen.
'This government, having tried to demolish the data by saying it meant half of all doctors are mad, is now convinced that there is a hard economic case.'
As a result, the government had agreed to take over the partnership on the health of the NHS workforce convened by the Nuffield Trust, in response to growing evidence of ill-health.
The partnership's review found that work-related stress among doctors was significantly higher than for equivalent professionals.
It ranged from anxiety through emotional exhaustion to clinical depression and suicide.
The same picture emerged among nurses and managers. Stress levels for health service managers were higher than for non-NHS managers, and highest among women managers.