Jeremy Hunt, secretary of state for health, was warned 18 months ago about a loophole that allowed foreign nationals to get treatment in their home country and charge it to the NHS.
The report was commissioned by Hunt, published in October 2013 and brought to light by a Daily Mail investigation.
It found that migrants were applying for European Health Insurance Cards (EHIC) in the UK, and then could receive treatment free in their home country.
The EHIC cards are intended for British people who need urgent medical treatment while they are overseas in Europe.
The 239 page Department of Health study was titled Qualitative Assessment of Visitor and Migrant use of the NHS in England: Observations from the Front Line.
The Department of Health has been contacted for comment.