The Royal College of General Practitioners (RCGP) warned against introducing reforms that could put doctors in an "invidious position of being the new border agency", after reports that the Health Secretary will "crackdown" on abuse of public health services.
The NHS bill for treating tourists, estimated to be up to £200 million, will be tackled as part of reforms being outlined by the Health Secretary on Wednesday.
Chairwoman Clare Gerada said:
GPs must not become a new 'border agency' in policing access to the NHS. GPs have a duty of care to all people seeking healthcare and should not be expected to turn people away when they are at their most vulnerable.
It is important to protect individuals and public health and General Practice must remain the main access to health care within the NHS.
Jeremy Hunt has said that he would like to see a coordinated approach to protecting the NHS from "costly abuse".
Discussing health reforms, due to be formally announced on Wednesday, Mr Hunt said: "No one expects health workers to become immigration guards and we want to work alongside doctors to bring about improvements, but I'm clear we must all work together to protect the NHS from costly abuse.
"We want a system that is fair for the British taxpayer by ensuring that foreign nationals pay for their NHS treatment.
"By looking at the scale of the problem and at where and how improvements can be made we will help ensure the NHS remains sustainable for many years to come."
Loopholes that allow migrants to wrongly access free UK health care will be closed under a crackdown on abuse of public services next week, Jeremy Hunt will announce.
The NHS bill for treating tourists, estimated to be up to £200 million, will also be tackled as part of reforms being outlined by the Health Secretary on Wednesday.
Ex-pats, who currently face paying for care if they live permanently overseas, are set to be given guaranteed access to free NHS healthcare, but only once they have paid 10 years of national insurance contributions.
The changes are part of a government wide push to cut down on abuse of British services but doctors warned they feared being turned into a "form of immigration control".