NHS hospitals are set to start advertising to attract patients for the first time under a new marketing code to be published by the Department of Health.
The draft code says the NHS needs to give "reliable information" to help patient choice. But unions have hit out at the plans, calling them "ridiculous".
The code will not put a limit on the amount of money hospitals can spend, but it is expected to say too much spending could affect the reputation of the NHS.
Dr Gill Morgan, chief executive of the NHS Confederation, said publicising information on everything from operation results to car parking was a vital part of giving patients choice.
She said: "We are trying to change the NHS from being a service where you get what you're given really, to a service where patients are much more able to choose what they want.
"Hospitals need to understand what patients want, and secondly they need to make GPs – and patients in some cases – aware of what is actually available."
But the British Medical Association (BMA) has said spending money on advertising would mean less money for patient care.
Dr Jonathan Fielden, chairman of the BMA's consultants' committee, said the NHS was forced to compete against private providers because of government reforms.
"NHS hospitals will have no option but to invest in marketing tactics, such as advertising, if they are to survive against private firms, who will already have large marketing budgets and considerable expertise in selling themselves.
"It is a sad indictment of government policy to consider spending public money on advertising NHS services when hospitals are having to make cutbacks in patient care and compulsory redundancies to save money."
Health service union Unison said the idea that hospitals should spend taxpayers' money on advertising instead of on treating patients was "ridiculous".
"It is the government's obsession with competition and choice that is forcing hospitals to set aside common sense and waste money in this way," it said.