Primary care trusts (PCTs) are not meeting official-out-of-hours patient care standards, suggests research carried out by the Liberal Democrats.
They say a third of PCTs are not meeting targets for clinical assessments over the telephone that assess immediate life threatening conditions.
More than four out of ten providers do not answer patients' calls quick enough, they add.
Another quarter of providers do not meet full standards in starting face-to-face consultations on time.
Liberal Democrat Shadow Health Secretary Norman Lamb said: "These very disturbing statistics show that many PCTs are failing to meet standards of care which the government itself says is crucial.
"It is critical that the public has confidence in the care that is provided to them when they can't see their GP. The danger is that people will choose to go to already crowded A and E units, which have seen a rise in admissions in recent years.
"The problem is that there is no way to hold providers to account for inadequate services; PCTs are not answerable to anyone for their actions.
"A patient's contract guaranteeing high standards of out-of-hours care and a system of local democratic control over services would keep standards high."