The Fire Brigades Union (FBU) has claimed fire engines are being used as makeshift ambulances to help overstretched A&E services.
It said the A&E crisis was a "direct result of the government's failed austerity agenda."
Matt Wrack, FBU general secretary, said “The public are being put at risk because the government have cut staff, resources and equipment in both the NHS and fire and rescue service.
“In certain incidences firefighters have been diverted away from doing their own work to cover for mistakes made by this government in the NHS.
“The knock on effect means that vital fire prevention work will be compromised as well as the ability to respond to other fire emergencies at a time of year where firefighters are expecting to deal with an increased number of flooding incidents across the UK."
Ed Miliband wants former nursing staff to be drafted in as part of a new five-point plan to ease the burden on accident and emergency.
Hospitals are saying there simply are not enough beds and trained medical staff for sick patients who need to be admitted.
With A&E waiting times slumping to their worst in 10 years, did your hospital make it on to the worst 10 list?