AMBULANCE crews began an overtime ban yesterday - and claimed the action would have an immediate impact on 999 response times.

A union official warned last night that the industrial action would disrupt the North-East Ambulance Service's (NEAS) ability to react to emergency calls quickly.

But management of the service - which covers a large chunk of the North-East from south Durham to north Northumberland - claims that contingency plans are in place to minimise disruption.

About 450 Unison members who work for the NEAS agreed to ban overtime after it was announced that staff will no longer be paid for breaks, although they will be expected to remain on standby.

The service, which has about 620 employees, relies on overtime as a way of covering for holidays, training or sickness.

Last night, Ray McDermott, Unison branch secretary, claimed that the industrial action had already had an effect. "Crew numbers are already down today and there will be more over the weekend," he said.

A significant number of unfilled posts would also put a strain on the service, he said, adding: "We have 16 vacancies in County Durham alone."

After an overwhelming vote for industrial action last week, it had been hoped that a compromise solution could have been hammered out in talks.

But the talks broke up without agreement, with no prospect of an early resumption.

Mr McDermott said that the dispute was initially with NEAS but they were later told that the Government had not provided funds to pay for paramedics' meal breaks.

"The two other emergency services get paid for their breaks, so why shouldn't we?" he said.

Mr McDermott predicted that the dispute could continue for some time. "This overtime ban will carry on as long as members tell me," he said.

The dispute arose from the NEAS's implementation of the Department of Health's Agenda for Change.

Simon Featherstone, NEAS chief executive, said in a statement: "While discussions to date have not resulted in an agreement, progress has been made on how the trust could achieve the 37-and-a-half-hour working week in line with the advice received jointly from the NHS Pay Modernisation Unit and Unison.

"Regrettably, despite this, Unison felt it had to continue with its planned action.

"We have contingency plans in place to minimise disruption."