The Healthcare Commission has called for national guidelines to ensure the safe management of volunteers who support ambulance services.
The move follows an investigation at Staffordshire Ambulance Service trust in January which raised concerns over the management of its community first responder scheme and led to a national survey of their use by the commission.
The snapshot showed the schemes, where lay people with basic life-support training respond to life-threatening calls alongside paramedics, are commonplace. Their use has expanded from mainly rural areas to adoption by all but one ambulance service in England.
A total of 10,158 people are signed up across 1,331 first responder schemes but attend only a small proportion - 1.8 per cent - of emergency calls, the survey found.
The commission uncovered widespread variation in the way the schemes were managed. All the volunteers are trained in resuscitation and can attend calls relating to heart attacks or chest pain, but training in other clinical interventions, use of drugs and attendance on other calls varies across the country.
Healthcare Commission investigating officer and report author Nicola Hepworth said: 'Guidance is needed to promote standardisation across ambulance services to support safe practice.'
She could not give details on the precise nature of the concerns at Staffordshire as the trust is still under investigation. She added that work has begun on guidance by the Ambulance Service Association, which is merging with the NHS Confederation next year to form the Ambulance Services Network.