The study, consisting of two reports by Creative Research and Prederi, was released as MPs prepared to debate the immigration bill later on Tuesday, which would introduce a £200 healthcare surcharge for temporary migrants.
The DH also plans to establish a new system to recover costs, which aims 'to tackle this issue and deter abuse of the system'.
RCGP chairwoman Dr Clare Gerada said GPs 'should not be expected to police access to healthcare', while GPC chairman Dr Chaand Nagpaul said there was limited evidence of overseas visitors ‘consuming large parts of the NHS budget’.
'Based on assumptions'
The DH-commissioned report estimates that £388m is spent by the NHS each year on visitors who should be charged, and between £70m and £300m on so-called 'health tourists'.
The DH estimates that with £200m gained from the surcharge, £388m from charging visitors, and the deterrent effect on health tourism, total savings will add up to £500m.
Previous official estimates put the cost to the NHS of overseas visitors at around £20m.
Dr Nagpaul said: ‘The government’s estimates are based on a number of assumptions that result in a figure significantly higher than previous estimates.’
GPs do not have the capacity to administer extended charging, he said, which would put additional strain on ‘already overstretched GP services’.
Dr Nagpaul added: ‘We must also be careful about creating a climate where some people are deterred from seeking treatment when they need it.
'Not only would this present a risk to the health of that individual, it could also prevent the NHS from identifying individuals with contagious diseases and result in further costs to the NHS should a patient's condition deteriorate to the extent they require more expensive emergency treatment later on.’
Dr Gerada welcomed research into the issue but said it was important to note many of the statistics in the report are 'based on approximate figures' and should be treated with caution.
Commenting on proposals to reclaim costs, she said: 'The most important issue continues to be implementation. It is imperative that GPs are not tasked with being a "new border agency" in policing the NHS.
'Limiting access to NHS services will fundamentally change one of the founding principles of general practice – that healthcare is free at the point of need.
'GPs have a duty of care to all people seeking healthcare, and should not be expected to police access to healthcare and turn people away when they are at their most vulnerable.'
She said the college 'strongly opposed' the extra administrative duties for GPs and practice staff that could be created as a result of the proposals.
Health secretary Jeremy Hunt said: ‘With the NHS already under pressure from an ageing population, it cannot be right that large amounts of taxpayers’ money is being lost through treating people who should be paying from foreign countries.
‘These independent reports prove this is a serious problem that the government was right to address. We are confident our new measures will make the NHS fairer and more sustainable for the British families and taxpayers it was set up to serve.’
Labour’s shadow health secretary Andy Burnham said the announcement was ‘more about spin than substance’.
‘The government’s own report undermines their headline-grabbing figures, admitting they are based on old and incomplete data.'
He said: ‘Labour would not support changes that make doctors and nurses surrogate immigration officials.’