David Cameron has defended his proposal to penalise hospitals for each patient who picks up an infection.
Mr Cameron says "payment by results" is the best way to tackle infections
In a speech, he said English hospitals should lose part of their tariff for each patient if that person contracted MRSA or Clostridium difficile.
But the British Medical Association said it would put hospitals off treating the most vulnerable patients.
Mr Cameron told the BBC "payment by results" was the best way to ensure NHS staff prioritised infection control.
In a speech on Wednesday marking the 60th year of the NHS, Mr Cameron said his party had an opportunity to replace Labour as the "party of the NHS".
He said the Conservatives would differ from the government's "top down" approach and said fining hospitals for not meeting infection targets was not working - instead their payments should be docked for each patient who became infected during treatment.
But Dr Laurence Buckman, chairman of the BMA's GP committee, told BBC Radio 4's Today programme: "That means that what will happen is that patients will be selected so hospitals won't admit people who look like they might get a complication afterwards - that means people who are chronic sick, people who have various cancers.
"How are you going to manage people on chemotherapy, who often get infections during the course of their treatment? Are you just not going to have them in the hospital?"
Payment by results
Mr Cameron told the BBC infection levels were "unacceptable" and were not going to be resolved with "top-down edicts and targets from Whitehall".
"We have got to make sure every hospital, every service, is prioritising this and the best way to do that is to make it part of the payment by results system."
He added: "That will mean that every doctor, every nurse, every ward sister, the management of the hospital will be absolutely thinking of infection control first and foremost."
Niall Dickson, chief executive of the health think tank the King's Fund, said Mr Cameron's speech had demonstrated a "degree of ambition which the Conservatives have not demonstrated since the NHS began".
But he said there was little difference in the analysis and solutions for the NHS between Labour and the Conservatives' approach.
Mr Cameron responded that while there were similarities in some of the details of policy, there was "quite a big philosophical difference" between the parties.
He argued that Prime Minister Gordon Brown favoured a "big top-down, state-centralised targets" approach while he favoured a "totally decentralised system", adding, "|What I want to do is put power in the hands of patients."