Nurses have overwhelmingly rejected Tory plans for a patient passport scheme.
The idea found little favour with nurses
Under the plans, patients could either use the NHS, or get the government to pay 60% of their private healthcare bills.
The Conservatives say the scheme would improve patient choice and create more patient-centred services.
But 95% of delegates at the the Royal College of Nursing congress in Harrogate voted against the proposals.
At last year's congress, RCN members rejected any creeping moves to privatise the NHS and warned against increasing bureaucratic workload of primary care physicians.
This year, members argued passports would cause the same problems, and potentially widen the gap in quality between hospital services.
Speaking against the proposal, Donna Cantrell, a staff nurse at Hartland's Hospital, Cheddington in Staffordshire, said: "Patients will be able to chose where they receive treatment and methods will be put in place to reward the most popular hospitals. This can only lead to poorer services in the less popular hospitals.
"And who will use the less popular hospitals? The elderly, people without passports, and those who are worse off in society."
She also warned that GPs would have to spend more time explaining treatment options and less time treating patients.
Andrew McGovern, of the RCN's East London branch, said: "It is not really a passport at all. It's an exit visa from the NHS for everyone with the ability to pay.
"It's a scandalous subsidy paid out of taxpayers' money to help the better-off jump the queue."
Dr Beverly Malone, RCN general secretary, echoed the cautions and welcomed the no vote.
"It seems like the possibility is there for those who have got resources to be able to use it very effectively but those who are trapped geographically or don't have the resources to travel, then they would be in a very different situation," she said.
Shadow secretary of state for health and education Tim Yeo said the Conservative party would push ahead with its plans despite the disappointing vote outcome.
"We clearly have a bit more persuading to do. The period between now and the election will be spent explaining the benefits of the passport," he said.
He said the system would provide greater patient choice, and not at the cost of quality or access by poorer patients.
"I believe people who make decisions, in consultation with their GP, have access to good information about the alternatives. But of course most people will prefer to go to the hospital that is closest to them.
"And there is a direct benefit to other NHS patients if someone chooses to use the passport to go into the independent sector everyone else on the waiting list moves
up a place."