Epsom and St Helier hospitals are facing a £4.8m fine for failing to hit infection reduction targets - the equivalent of £65,000 a day since the start of the year.
Since April last year 61 patients - 29 at Epsom and 32 at St Helier - have developed Clostridium Difficile, a bacterial infection which commonly occurs in patients who have taken antibiotics, and is transmitted via contaminated surfaces.
The trust's target, set by the Department of Health, was to keep the number of C Difficile cases below 53 this financial year.
In January the hospitals had recorded 55 cases and faced a £1.4m fine but with six more cases the fine has massively increased.
Two more cases in the next fortnight could have cost it almost £500,000 each but the maximum fine has now been capped at £4.8m "following negotiations with our local primary care trusts", according to a trust spokeswoman.
A spokesman for the Department of Health (DoH) said the PCTs are responsible for enforcing any fines - which are "non-negotiable".
He said: "The fine is non-negotiable, but how it is spent is.
"The money can be withheld money from the hospital, they can ask for it be handed over, or enter into a dialogue with the hospital to see how service improvements can be made using the money."
The hospital trust spokeswoman said "a raft of measures" are in place to tackle C Difficile cases, including training staff about infection prevention and control, improving the cleaning of wards, and reminders about good hand hygiene.
Four dedicated nurses and three pharmacists have also been employed, as well as a review conducted on the trust’s antibiotic prescribing policy.
The trust has seen a 75 per cent overall reduction in the number of cases of C Difficile in the last five years.
The spokeswoman said: "The measures we have in place should be sufficient and fit with best practice.
"However, we operate a zero tolerance policy towards healthcare associated infections and one infection is too many.
"We will continue to monitor our key areas of practice."
They said a "significant number of other hospitals including others in South West London and Surrey" have missed or are very close to their targets.
But Kingston Hospital said it has recorded just 21 cases of C Difficile and is not facing a fine.
St George’s Hospital, in Tooting, said it had had 60 cases after treating 66,211 in-patients and a spokesman said it "does not expect to be fined".
Despite the fine, the projected deficit at Epsom and St Helier hospitals for the end of this financial year is now £12.1m - down from the £19.4m originally estimated.
Chris Grayling MP said: “It’s not good to have an increase of infections in hospitals, so reducing C Difficile ought to be a priority for Epsom and St Helier to sort out.
“I hope there won’t be the question of a fine next year.”
Local health campaigner Bob Mackison added: "It is very sad that they are facing any fine at all when both hospitals are under threat.
"The staff don’t know whether they are coming or going. If there has to be a fine it should be the management that pays it."