Dorset's police helicopter service has one of the top ten quickest response times, despite new information revealing helicopters across the country are taking too long to reach crime scenes. 

A watchdog has found that police helicopters take so long to get to incidents that thousands are called off mid-air because they are already over. 

More than 40 per cent of call-outs nationwide last year were cancelled because the incident was over before air support had arrived, according to an independent inspection.

In many areas it took more than half an hour for a helicopter to reach the scene.

However, the report by Her Majesty's Inspectorate of Constabulary and Fire and Rescue Services reveals that Dorset has the eighth quickest time in the country at 22 minutes. 

London's Metropolitan Police helicopter is the fastest with a response time of 10 minutes and Cumbria has the lowest response time at 66 minutes. 

Superintendent Nikki Leaper, Alliance Specialist Operations, said: "Dorset Police receives a good service and value for money from the National Police Air Service (NPAS).

"Air support is accessible from local NPAS airbases at Bournemouth, Exeter and Filton which means we achieve good response times. When a helicopter is off line we can utilise another from a nearby base.

"In Dorset national air support is called upon for a range of incidents from missing person searches, crimes in progress and local priorities."

The report reveals that the number of helicopters in the fleet has been reduced from 33 to 19 since 2009. It calls for a major overhaul of NPAS or for it to be replaced, saying the service "in its current form is financially unsustainable."

Forces in England and Wales were responsible for their own air support until the national collaboration was created in 2009.