The UK paid out more than £647m to European countries for the health costs last year, receiving just £49m in return, according to Labour MP John Mann.
The discrepancy was revealed in a department for health response to Mann, who sits on the Treasury Select Committee.
Notably, Mann said the UK pays France over £147m and received just over £6m back, while the UK gives Germany over £25m and gets just £2m back.
"Sorting this scandal out in itself would transform the financial situation of the NHS. This is a shambolic state of affairs and we are being played for fools," Mann said.
He added: "This is money that should directly be going into the NHS and it would make a huge annual difference to its finances."
The comments from Mann come ahead of the impending referendum on 23 June.