Ambulances were dispatched unnecessarily on more than two million occasions in a year because of a “skewed” approach to performance management caused by response time targets.

A National Audit Office report has found the focus on time targets did not “encourage resource optimisation” and often led to duplicate ambulances being sent to the same incident. In 2009-10 ambulances were dispatched 10 million times but only actually attended an incident on 7.9 million occasions.

The review backed the government’s decision to scrap the category B target requiring ambulance services to attend 95 per cent of serious calls within 19 minutes. It was replaced in April with 11 indicators to measure quality and encourage more appropriate forms of treatment.

The NAO also estimates increased use of treatment at the scene or over the telephone could save ambulance trusts £110m a year and the rest of the NHS up to £165m.

But NAO auditor general Amyas Morse said savings and improvements would only be made if the urgent and emergency care system worked “more coherently”.

The report found a fifth of handovers at emergency departments took more than the recommended 15 minutes. It recommended that commissioners focus more on incentivising both hospitals and ambulance services to reduce handover times.

It said the Department of Health needed to establish how the call connect system, which starts measuring the response time as soon as the call is answered, can be made more flexible. HSJ understands senior ambulance officials have been lobbying the DH to change the system so the time starts once a call has been categorised.

The report found ambulance services collectively spend £80m on overtime and have high sickness absence rates. It found spend per call varied from £144 at North East Ambulance Service Trust to £216 at the Great Western Ambulance Service Trust. It recommended that services work together to share best practice.

However, the review warned this collaboration could be inhibited if “services envisage being in competition with one another in the future”.

Ambulance Service Network director Jo Webber said ambulance services recognised the need to address variation and share information “more effectively”.