Ambulance crews in the West Midlands lost more than 5,000 hours in a year waiting outside hospitals to hand over responsibility for patients.
Paramedics aim to transfer patients to hospital care in a maximum of 30 minutes, but newly-disclosed figures show crews are being delayed from responding to further 999 calls by waiting, often for more than an hour for medics to take over.
More than 9,700 hours were lost over two years at the region's hospitals, costing the service about £600,000.
About 1,688 hours were lost at New Cross Hospital in 2010, the highest total in the Black Country and Staffordshire, up from 1,218 hours lost in 2009.
Russells Hall Hospital in Dudley saw more than 3,000 lost hours in 2009 and 2010 while 1,624 hours and 1,073 hours were lost in Sandwell and Walsall respectively.
At Stafford Hospital, 400 hours were lost in 2010 — more than double the 194 hours clocked in 2009.
The ambulance service has attempted to tackle delays by appointing liaison officers to tackle problems as they arise.
It has also launched a computer system showing how many ambulances are heading for hospitals and how serious each case is — allowing the hospital to plan ahead.
Spokesman Chris Kowalik said: "We work very closely with each of the hospitals to manage the flow of patients from the arriving ambulances into the hospital so that any delays are kept to the absolute minimum.
"Regular meetings are held to try to improve the systems in each hospital and we have seen a number of improvements."
New Cross Hospital said it has asked the ambulance service to divert more low risk patients to walk-in centres instead of A&E.
Tim Powell, from the Royal Wolverhampton Trust, said: "Patient safety is our number one priority, and if seven ambulances turn up at the same time, we must provide immediate care to those who need it most, but unfortunately, this can cause delays for the less urgent cases."
Sally Lavender, of the Dudley Group of Hospitals, said: "We prioritise all patients who need urgent, medical attention."
Maggie Oldham, from Mid-Staffordshire NHS Foundation Trust, added: "We currently have some of the best handover times in the region."