A committee of Welsh Assembly members has said that a contract that gave GPs an average 25% pay rise in its first two years has not delivered value for money.
A cross-party report said that despite the fact there have been some improvements since the General Medical Services contracts were introduced in April 2004, they have not yet reached their full potential.
The system changed the way GPs' incomes are calculated and cost the Welsh NHS an extra £131m in 2005-06, but the Assembly's Audit Committee said some patients may not be finding it any easier to see their doctor.
And it is calling for the government to put more emphasis on improving patients' access to doctors, and on monitoring performance.
The committee's Conservative chairman, David Melding, said: "The new contract has delivered some benefits for patients in Wales, but more needs to be done to ensure that all the potential benefits are realised, or it will not represent value for money.
"The committee has made a number of recommendations to the Welsh assembly government and I hope these are acted upon so that improvements can continue and patients receive the service they deserve."
An assembly government spokesman said: "The health minister welcomes the report and will carefully consider its findings."