The new EU treaty will take some of the government's control over the NHS and could create a two-tier system that will benefit the rich, MPs were told.
The treaty aims to replace the failed EU constitution
Ex-health secretary Frank Dobson said a new EU directive would allow patients to travel to Europe for treatment and claim back costs on the NHS.
"It would clearly give a leg up to the well-off to the disadvantage of everyone else," he said in the Commons.
But Europe Minister Jim Murphy said healthcare was for EU states to decide.
The issue was raised during the fourth day of topic-by-topic debates on the Lisbon Treaty - signed by Gordon Brown in December - but which has yet to be ratified by all parliaments across the EU.
Mr Dobson claimed that "neo-liberals" in the European Court and European Commission were increasingly exposing healthcare to "internal market forces".
"It would appear that our National Health Service is, and will remain, the exclusive responsibility of the British Government, but it isn't and under the Lisbon treaty, it won't," he said.
"All that apparent protection for our sovereignty, provided in both the old and new treaties, simply isn't there because it turns out some parts of the treaties are more equal than others."
Opponents fear the draft directive will increase "health tourism" and undermine the NHS by allowing patients to jump queues and undertake expensive procedures which they might not be entitled to in the UK.
Mr Dobson said he believed this would benefit the wealthy.
"The well-off will be able to pay in advance and wait to be reimbursed, they will be able to pay top-up costs if they need it and they will be able to afford the costs of travel," he said.
"Badly off people will not be able to do any of those things."
But Lib Dem treasury spokesman Vincent Cable questioned why it was right for people to buy a horse, or travel or exchange goods in Europe, but not to try to pursue a higher life expectancy in a country that has better cancer treatment.
"Common sense would demand that is a reasonable expectation of an integrated market," he said.
"This is going to happen and as long as the basic frameworks of the NHS remain intact, I don't see anything fundamentally wrong with enlarging the concept of a single market to include health."
But Mr Dobson hit back: "If you buy a house in Europe, you're spending your own money.
"If you are getting NHS treatment in Europe you are spending somebody else's money that might have been spent in the NHS."
However, Mr Murphy stressed that the treaty was "clearer than ever before that member states remain solely responsible for organising, delivering and making decisions about the allocation of resources to their health systems.
"Article two says it is for individual member states to organise and deliver the health systems.
"Those words are new in the Lisbon treaty. They helpfully clarify that the allocation of resources in public health systems is for member states to decide."