Firefighters responding to medical emergencies are "ill-equipped" to deal with some of the 999 calls they attend, a fire chief has said.
Fire crews in some areas work as ambulance "co-responders" where they attend medical emergencies to stabilise a patient before paramedics can arrive.
The Fire Brigades Union (FBU) told The Times crews sometimes arrived to "major trauma" which they did not have the training to deal with.
John McGhee, FBU national officer, said: "We've had a number of incidents where people have thought they were attending someone who has a heart attack, only to get there and discover a major trauma.
"We've not got the medical training to deal with somebody impaled on a fence.
"If we get to an incident where we are as much use as a car of football fans, then it raises serious concerns."
Katherine Murphy, chief executive of the Patients Association - a charity campaigning on behalf of patients, blamed underfunding of the health service for the problem.
She said firefighters should not be asked to do the job of a paramedic with only first aid training.
The Department of Health told The Times the decision on how best to respond to 999 calls was the responsibility of ambulance trusts, but it supported better communication between the emergency services.