The government has agreed to a review of how the EU working time directive will impact on junior doctor training.
Unions have warned that the 48-hour weekly limit, which is due to come into force for the NHS in August, could harm the quality of training.
Health Secretary Alan Johnson has now asked Medical Education England, which advises on doctor training, to look into the issue.
But doctors and opposition parties said the review was happening too late.
Junior doctors have already been reducing their hours in preparation for the change.
The British Medical Association has warned that this has left medics with less time too study because most of their working hours have to be spent on the wards looking after patients.
Mr Johnson said there has been no suggestion that training has suffered so far.
But he added: "Given the concerns raised by some it is important that there is an independent and objective assessment into whether the introduction of the directive will necessitate changes to the current system of postgraduate medical training."
Dr Andy Thornley, chairman of the BMA's junior doctors committee, said the review was coming a little late as ministers had had over a decade to prepare.
"Junior doctors currently deliver a large proportion of service in hospitals, but they also need time to train to become the consultants and GPs of tomorrow."
Shadow health minister Stephen O'Brien added: "The review is too little too late. For months, the government has stubbornly refused to recognise the impact of the directive on the nation's doctors."