Speaking after the monthly GPC meeting in London last week, GPC negotiators warned that funding for out-of-hours services was already tight.
They feared that diverting cash to fund NHS 111 could put out-of-hours services at risk.
'We have one main concern: how will (NHS 111 services) be paid for when the pilots end?' GPC chairman Dr Laurence Buckman said.
'They appear to cost more than existing provision, especially when that is NHS Direct. The concern is that it will come from the out-of-hours service, they will take money to provide NHS 111.'
GPC deputy chairman Dr Richard Vautrey said: 'Out-of-hours organisations are already very stretched.
'If you remove any further funding it will put the service at risk.'
Dr Buckman added that the quality of NHS 111 services developed in pilot areas was widely variable.
'We have concerns about how some of the pilots are operating in some areas,' he said. Across England the situation was 'a mosaic', he added, with quality poor in some areas but good in others.
Dr Buckman said that even in some neighbouring pilot areas which appeared to be operating the same NHS 111 model, GP satisfaction with the scheme was highly variable.
Dr Vautrey explained that the higher costs associated with NHS 111 compared with NHS Direct often stemmed from the service's aim to deal with patients in a single phone call.
He said that in areas where the service did not use experienced clinicians to triage calls, this aspiration could increase costs. Call handlers were more likely to call in an ambulance, for example, he pointed out.
Some parts of the country had seen a 'dramatic rise' in ambulance usage, while others had seen a drop, he said.