GPs in Scotland are struggling to cope with the country's rising population, the British Medical Association (BMA) claims.
And the crisis could eventually see patients turned away from surgeries, it added.
BMA Scotland said the government must provide extra funding if GPs are to cope with the pressure on the health service from workers from places such as Poland and other Eastern European countries.
Family doctors have seen their patient lists rise due to initiatives such as the Fresh Talent policy, which is designed to encourage people to live and work in Scotland.
But surgeries in the Lanarkshire and Grampian areas are now so stretched they have to turn new patients away, the BMA said.
Dean Marshall, chair of BMA Scotland's GPs committee, who runs a surgery in Dalkeith, Midlothian, said the former Labour-led Executive did not address the problem of the rising pressure on GPs, and that the new SNP leadership is heading the same way.
He said: "Scotland's population has risen significantly in the last five or six years on the back of the previous administration encouraging people to come.
"Currently, there is no mechanism to increase the funding for GPs who have been treating more and more patients for less funding.
"This is not something that can continue. Doctors are in a really difficult position and they are going to have to close their lists.
"It's happening already in some areas and it cannot continue."