More than 80 complaints have been made about Cornwall's new privately-run out-of-hours GP service.
KernowDoc, run by GPs, had provided cover since the 1990s but in April Serco was awarded the contract.
GPs said they were worried about how long it took for Serco's doctors to attend to patients and the time it took for calls to be returned.
Health officials admitted there were some teething problems but described the level of complaints as "average".
GP Phil Dommett, chairman of the Local Medical Committee, said it appeared there were not enough doctors employed.
"They were given the remit to use a more effective and efficient service and not use so many doctors," he said.
"Cornwall is a large county and there are peaks and troughs in demand and doctors I've heard from are, on occasion, quite worried there are gaps in the service."
Serco was commissioned to run the service by the county's primary care trusts.
Dr Jon Tilbury, who speaks for the PCTs, denied it was a cut-price service.
"It meets the national quality standards, there have been some teething problems in the transition period, I am very confident those will be ironed out.
"It is a cheaper service than KernowDoc but I don't think that necessarily compromises quality."
Michelle Preston, Serco's operations director for its out-of-hours service, said its service was being reviewed constantly.
"It is difficult with an out-of-hours service sometimes to match demand and capacity.
"Peak times vary and in Cornwall the summer pressures do give us some challenges but we are constantly reviewing our activity and making sure we have clinicians on duty to meet those demands."