Scotland's ambulance service is chronically short of funding and struggling to cope, according to GPs.

Doctors are expected to demand the Scottish Government increases the money it gives to the service at a major conference next week, amid a massive rise in emergency calls.

One doctor said a huge burden was being placed on paramedics and ambulance technicians to manage situations they were "not best trained for".

This, he said, followed changes to the level of GP cover available to help patients outside surgery hours which has left communities "doctor light".

Last year a report revealed the Scottish Ambulance Service (SAS) had missed its target for reaching three-quarters of emergencies in eight minutes.

Now fears about the level of ambulance cover in communities are being put forward at a GP conference, organised by the British Medical Association, in Glasgow next week. Motions say the service is struggling to meet its obligations because of chronic underfunding.

Dr Brian Fitzsimons, a GP in the Highlands and chair of the medical committee that is raising concerns, said: "With the change to the out-of-hours service, it is not uncommon to find there will be no ambulance from Wick to Dingwall because they will be out on emergencies. Stations will be busy and something else will happen.

"The cover has stretched, with the change in out-of- hours, to breaking point."

As a rural GP, Dr Fitzsimons said his call-outs have increased and the majority are during evenings and weekends.

"Paramedics are having to do things doctors had to do before," he said. "We are putting a huge burden on guys who are doing a fantastic job, but a job they are not necessarily best trained for."

The number of times ambulances crewed by one person are dispatched to emergencies in the Highlands is a concern. Dr Fitzsimons said this was no longer a rare occurrence.

Health Secretary Nicola Sturgeon said: "The Scottish Government is committed to ensuring the Scottish Ambulance Service provides safe, efficient and effective services to patients across Scotland."

She said their revenue allocation for 2008-09 was £183.4m - an increase of 3.15%.

A spokesman for the SAS said: "We have to provide a service within finite resources and currently deliver an average response time of around eight minutes for all of Scotland."

GPs are being asked to consider taking industrial action over changes to their new contract at the BMA conference.