A hospital trust was left with an unexpected £5.6m bill for non-emergency patient transport after commissioners underestimated the cost, a report has revealed.

The document, by consultancy PwC, on the causes of Imperial College Healthcare Trust’s deficit, said the organisation “incurred £12.1m of non-emergency patient transport service costs in 2015-16, only receiving £6.5m from clinical commissioning groups”.

It said the trust subsequently renegotiated for additional funding for 2016-17 “to more accurately reflect the non-emergency patient transport need”.

The trust’s contract with DHL Supply Chain started in 2011..

The trust is currently running a procurement exercise for a new patient transport contract, due to start in July.

A spokeswoman for the trust said: ”The trust provides non-emergency patient transport, on behalf of commissioners, to patients where clinically appropriate and this should be funded by commissioners. There was a known shortfall in this funding which has since been addressed so income more accurately reflects the costs of providing this service.”

The PwC document, released this week under the Freedom of Information Act, comes after the national patient transport market was complicated by two major providers leaving the sector.

In north west London, the insolvency of the company Private Ambulance Service in September caused significant operational problems for London North West Healthcare Trust, which had to organise a replacement at short notice.

The patient transport market in London is thought to be worth more than £50m.

The PwC report said Imperial’s underlying deficit in 2015-16 was £53.6m – £14.8m of which was down to under recovery of income on issues like patient transport, high cost drugs and devices and not claiming best practice tariffs.