David Cameron has defended Conservative proposals to financially penalise hospitals where patients catch 'superbugs'.
The Conservative leader's comments come as medical experts warn the policy could discourage hospitals from treating the most vulnerable patients.
Mr Cameron unveiled the controversial proposal yesterday as part of a pledge to make the Tories the "party of the NHS". He proposed NHS hospitals should not be paid in full if patients catch superbugs such as MRSA and Clostridium difficile while undergoing treatment.
The charge would replace the current scheme whereby hospitals are fined for an unacceptably high overall infection rate, rather than penalised on a case-by-case basis.
But the British Medical Association (BMA) warned today such a system risked discouraging hospitals from treating the most vulnerable patients.
Speaking to the Today programme, Laurence Buckman, chairman of the BMA's GP committee, said: "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?"
Mr Cameron insisted, however, that payment by results would encourage all NHS staff to make infection control a top priority.
He told the BBC: "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.
"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."
The government has already dismissed the Tory leader's call, claming Mr Cameron has ignored legislation already proposed.
Health secretary Alan Johnson said: "We are already taking powers to fine poor performing hospitals, with the pledge to reinvest that money back into the local NHS."
He argued that abolishing top-down targets risked allowing the NHS to "take its eye off the ball".
The NHS is shaping up to dominate the political agenda in 2008, with both the main party leaders starting the new year with high-profile hospital visits.
Early in his premiership Mr Brown identified infection control as a major concern of voters. In response, the government announced plans to require every hospital to undergo a "deep clean".
However, like the Tory proposals, this was rubbished by experts who claimed it would do little to tackle superbugs.