Harry Dunn, the teenager who died after his motorbike was in a collision with a car driven by the wife of a US diplomat, lay by the side of the road for 43 minutes before an ambulance arrived because the urgency of his case was “wrongly categorised”.

The 19-year-old died in hospital. His motorcycle had been hit on 27 August this year near RAF Croughton, Northamptonshire, in the UK, by a car being driven by Anne Sacoolas on the wrong side of the road.

Harry Dunn: 'Informal' talks begin over possible extradition of Anne Sacoolas Read more

The ambulance service listed his injuries as category 2 requiring an ambulance within 40 minutes. If he had been classified as category 1 the ambulance should have arrived within seven minutes.

The first call made by a witness of the collision was put in category 2, which refers to incidents of a potentially serious condition and which estimates a waiting time of 40 minutes for patients.

The miscategorisation was revealed when Dunn’s parents met officials from the East Midlands ambulance service to discuss how their son died and the quality of the care provided by the NHS.

Emergency call handlers decided to classify the accident as not life threatening, despite Dunn “breaking every major bone” in a collision described as a “crash fireball”.

The delay in the arrival of paramedics was raised by the shadow foreign secretary, Emily Thornberry, in Foreign Office questions in the Commons on Tuesday.

On Wednesday Dunn’s family met Richard Henderson, chief executive of East Midlands Ambulance Service, and Nichola Bramhall, the service’s director of quality, to discuss the delay.

The family’s spokesman, Radd Seiger, said Dunn’s parents, Charlotte Charles and Tim Dunn, were full of praise for the work of the paramedics on the scene, but said the delay in getting to their son was “worrying”.

Seiger stressed that the Dunn family had expressed their deep gratitude to the NHS staff who had battled to save their son’s life, adding that they had had a very warm meeting discussing the challenges frontline staff faced and “which were likely to have played a part in the delay on the night of the collision”.

Henderson and the family agreed that a meeting could be arranged as soon as possible between the Dunns, local leaders of the NHS, and himself to start a dialogue “hopefully with a view to securing positive changes to the complex system involved in the delivery of services”.

Seiger said the family felt it was the first positive meeting they had had with a public agency since the death of the teenager.

Addressing the reasons given for the paramedics’ delay, the spokesman told PA Media: “Mr Henderson made the point that actually, because of the shortage of crews, whether it was a category 1 or category 2 wouldn’t have made a difference because the doctors were far away. At that point there were lots of tears because the family wanted to know – was he frightened? He was clearly conscious and by the time Tim got there he was still talking. From what they were able to share with us, there were no double-crewed vehicles readily available.”

The Dunn family are seeking judicial review of the Foreign Office decision to grant Sacoolas immunity, and are also seeking to make a civil damages claim against Sacoolas in the US.

Northamptonshire police have interviewed Sacoolas in the US and have left it to the Crown Prosecution Service to decide whether to bring charges. Donald Trump said he would decide whether Sacoolas should return to the UK when he had seen the full facts.