A new computer system at the London Ambulance Service has caused major delays in answering emergency calls.
Staff at the service took more than 20 minutes to answer calls at the height of the difficulties in the early hours of Saturday 25 November. The usual response time is five seconds.
London Ambulance dismissed press reports that it was facing another IT crisis like the disaster that hit its new control room software in 1992.
A representative said there were no technical problems with the new system, but acknowledged that the service struggled to deal with an estimated 1,000 calls during a busy eight-hour period over the weekend of 24 and 25 November.
Control staff confirmed to Computer Weekly that the systems are functional but said staff shortages and difficulties learning the system produced the problems.
"It was the suggestion of the staff that they wait until after Christmas to implement the system," said a Unison trade union representative at London Ambulance Service. "The problems occurred only three days after the new system was put in."
Geoff Martin, director of pressure group London Health Emergency, said, "There have to be some serious questions asked about how the system has been introduced.
"No matter how good and effective the computer system is, there will be problems if you haven't got the staff numbers that you require," he added.
Ian Tighe, director of technology at the service, said, "I am saddened if some people think that we haven't done enough but if the issues are about training and staffing, then I would love to hear from them."
He added, "We are bringing in additional resources in our control room and extra paramedics in December and January."
The Advance Medical Priority Despatch System was built by Salt Lake City-based software firm Medical Priority Consultants. It is designed to prioritise the allocation of ambulances to emergency calls. It replaces an old-fashioned card-based sorting system, and is designed to integrate with Londong Ambulance Service's Unix-based command and control operation.
London Ambulance was heavily criticised when its computer-aided despatch system crashed in 1992.