Freedom of Information requests by Pulse, a magazine for doctors, revealed the average unpaid debt for the provision of care to foreign nationals was £230,000 in the 35 trusts which responded.

The FoI requests showed St George’s Healthcare Trust in South London had the largest outstanding debts, totalling £2 million from £3.55 million invoiced to foreign nationals for health treatment from April 2009.

The group’s chairman Sir Andrew Green said: ”To allow such easy and potentially hugely-expensive access without any entitlement must be stopped at once, otherwise the NHS risks becoming the World Health Service.”

Last year, FoI requests from Tory MP Chris Skidmore showed £42 million in unpaid debts for treatment of foreign patients had been written off by primary care and foundation trusts.\

The Royal Wolverhampton Hospitals Trust collected 24% of the £419,000 owed to it, the figures showed.