The recommended vehicle waiting time stands at 15 minutes but the longest delay recorded in Wales, involved a patient waiting in an ambulance for six hours 22 minutes. Another in England recorded a five hour 51 minute wait.

The figures, reported by the BBC under the Freedom of Information Act, revealed the longest waiting times for 12 weeks between August and October.

During the period there were incidents every week of more than three hours waiting time in Wales. Scotland performed best of the three regions with the maximum waiting time recorded at two hours.

Linda Millband, a clinical negligence solicitor at Thompsons, said: “Pressures on the ambulance service and A&E departments are likely to increase during the winter period so these recent figures do not bode well.

“Paramedics cannot leave patients until they have been safely transferred into the care of staff at A&E departments. If a member of staff isn’t available, there is no choice but to keep patients waiting in ambulances.

“While patients wait to be seen inside the hospital, ambulances are not on the road responding to other calls, so the problem is two-fold.

“Not every patient is experiencing up to six-hour delays but to have these statistics on record clearly indicates that there are problems in the system which must be addressed to ensure a better standard of patient care.”