Doctors have said the free GP care scheme for five-year-olds and under, as proposed by the Government, will not be a "high-end" service because it will not be properly funded.
The National Association of General Practitioners said some GPs might not sign-up to the plan.
The NAGP, which initially welcomed the scheme, has now said that it believes the initiative will be merely an extension of the current medical card scheme.
Speaking on RTÉ's Morning Ireland, NAGP Chairman Dr Andrew Jordan that the budget of €37m for the scheme would mean it was not a high-quality service and some GPs might not sign-up to the plan.
Dr Jordan said: "We thought, in good faith, that they were going to announce a scheme that was likely to deliver a high-end service.
Unfortunately, in the Budget the figure of €37m was rolled out and we realised this was just an extension of the present GMS, which of course is not a top-end service, and therein lies the problem."
He said it would result in a two-tier system - full medical card and GP card - for five-year-olds and under.
Dr Jordan said it came against the backdrop of millions of euro being taken out of the Budget for the GMS scheme.
He said the GP care scheme for five-year-olds and under would be a separate contract and doctors could decide individually not to take it up.
Dr Jordan also rejected reports in some newspapers that GPs were still being paid for patients who had died or people who no longer use medical cards.
He said: "I can't see how it's true ... If you're going to say that, you're basically saying that the HSE is incompetent and I do not believe for a second that the HSE is incompetent ... they are on top of their game."
Dr Jordan also criticised reductions in funding for existing medical card schemes.
"The total GP budget to take care of the sick and vulnerable is €440m. This is quite catastrophic," he said.