Health trusts in the Bristol area spent more than £66 million filling staffing gaps in a 20-month period.

Figures obtained by the Post using the Freedom of Information Act show that more than 2-million overtime and agency hours were paid for to ensure that there was sufficient cover at the hospitals and ambulance service.

Trusts said that wherever possible they made their own arrangements to cover shifts rather than relying on outside agencies to fill the gaps.

And they all said that cover through overtime, their in-house, or bank, agencies or external providers was necessary to ensure the smooth running of health services.

Figures were gathered from North Bristol NHS Trust (NBT), which runs Frenchay and Southmead Hospitals, University Hospitals Bristol NHS Foundation Trust (UHBristol) which runs nine city centre sites, including the royal infirmary and children's hospital, Weston Area Health Trust (WAHT), which runs the general hospital in the seaside town, and Great Western Ambulance Service (GWAS), which provides emergency cover in the former Avon area.

Data was gathered for every month from April 2007 and November 2008. All the trusts use internal and external staff to fill gaps, from administration workers to doctors, to ensure the smooth running of their services, but the bulk of money is spent on medical staff, including nurses and doctors.

Hospitals locally now work with approved agencies to keep costs down and to maintain standards.

NBT, which is the biggest employer of the four health trusts, with about 8,800 staff, also had the largest bill to cover hours – £28.4m for 1,507,266 hours.

April 2008 was the most expensive month for NBT, when 69,529 hours were covered in-house at a cost of £1.2m, while agency staff were used for 24,040 hours, with a bill of £601,000.

Deputy director of nursing, Carol de Halle, said that March and April 2008 saw a rise due to the Department of Health's deep clean programme. She said the trust did not pay for agency staff unless the safety of patients was likely to be affected and they always opted for bank staff first.

Ms de Halle said: "The use of bank and agency depends on vacancies, recruitment, long and short-term sickness and maternity leave.

"It is a part of the way the health service runs at the moment. Having bank is very, very important and we know that in a big acute hospital we are going to get acutely ill people who need monitoring, care and attention."

UHBristol, with about 7,300 employees, had a total bill of £22.7m for 372,000 hours. The most expensive month was November 2008 when £711,193 was spent on agency (3,562.5 hours) and £829,819 (12,525 hours) through the bank.

Acting chief nurse at UHBristol, Pat Fields, said: "Everyone has temporary staffing measures in place.

"It is pretty predictable around holiday times, but then there are times when we have to open extra wards and we would look to staff them with bank rather than agency.

"If we know we have got people away, short or long-term, we will be putting requests into the bank and have a waiting list of those people expecting to be phoned."

GWAS spent £4.9m on 275,285 hours of staff overtime and £5.6m with 109,178 hours of agency time. The trust, which employs 1,466 full-time equivalent staff, had used agencies as a matter of course, but following a review of services last autumn the decision was taken to limit the use of external providers.

September 2008 was the most expensive month, with £630,348 spent on 11,832 agency hours and £328,178 on 17,879 hours of overtime. The trust was unable to provide details of agency payments for the first three months of 2007/08.

The nature of ambulance staff shifts means there are often a few days between shifts when crews can fill in without it having an impact on their work.

GWAS spokeswoman Victoria Eld said the trust had not had to rely on agencies so much since additional funding was obtained from local health trusts to employ more staff.

She said: "We target agencies in particular areas and specific types of work, such as low-category calls that do not necessarily need one of our fully trained paramedics, but also at peak times such as bank holidays when there might be an increase in demand.

"We try and plan gaps through overtime but we are never going to be able to turn off the tap and there are always going to be sudden peaks in demand."

WAHTemploys 1,800 staff. July 2008 was the most expensive month with 6,184 hours through the bank at a cost of £69,045 and £591,478 to agencies, although they did not provide a breakdown of hours paid to external bodies.

Spokeswoman Caroline Thomas said: "We always try to fill vacancies with bank staff and only if we are unsuccessful do we then approach the agencies. Sometimes we use agencies if the request for cover is made at very short-notice, because a member of staff falls sick, for example.

"We see an increase in the need for cover in the winter when we have an increase in patient activity and sometimes also in staff sickness."