Family doctors have already warned of being turned into ‘de facto border guards’, after hints that health professionals will be required to check eligibility for treatment.
Some experts have described such proposals as unworkable and it is likely to be many months before concrete proposals are unveiled.
As a result, the Immigration Bill is not expected to become law before restrictions on Romanian and Bulgarian migrants are lifted next January – the trigger for the crackdown.
Dr Judith Husband, the BDA’s chairwoman of Ethics, Education and the Dental Team, stopped well short of the criticism levelled by the Royal College of GPs.
But she said: “Any decisions must be underpinned by the principle that clinicians’ obligations to treat patients requiring urgent care, or who are not able to pay for it, are not undermined.
“It is also important that clinicians are provided with clear guidance about what is required so that any policy changes can be understood, implemented and communicated clearly, and that they are fully supported in introducing and enforcing any change.”
The fears were raised after wide-ranging measures to restrict foreigners' access to rented accommodation and health services were put at the heart of the Queen's Speech.
The Bill – widely seen as an attempt to tackle the rising UKIP threat – will not emerge until after months of Conservative-Liberal Democrat talks on the details.
In the Commons, David Cameron told MPs: 'For the first time, we will make sure that anyone not eligible for free health care foots the bill, either themselves or through their government. That will be the effect of the Bill.'
The comment raised the prospect of hospitals and surgeries being expected to check whether migrants are eligible for any NHS treatment they claim.
That may go further than the current requirement for patients to simply fill in a form stating they are entitled to NHS care.
However, ministers are also exploring making non-Europeans provide proof of private insurance – or pay an ‘NHS bond’ – before they can receive a visa.
Coalition tensions were laid bare when Vince Cable, the Liberal Democrat Business Secretary, said health professionals must not be expected to make any checks.
He said: 'That is not the role of doctors – doctors are there to provide medical care.'
Clare Gerada, chairwoman of the Royal College of GPs, said doctors must not be placed 'in the invidious position of being the new border agency'.
She added: 'GPs have a duty of care to all people seeking healthcare and should not be expected to police access, and turn people away, when they are at their most vulnerable.'
By parliamentary correspondent, Rob Merrick