Ministers knew of the botched handling of a clostridium difficile outbreak at an NHS trust five months ago and should have acted then, the Conservatives say.
An initial report on the findings was issued in early May
An initial report into errors at the Maidstone and Tunbridge Wells NHS Trust, where as many as 90 people died of the infection, was issued on 3 May.
Shadow health minister Andrew Lansley says the government should explain why it waited until October to take action.
The Department of Health says the report was only an "early outline".
It did not contain any conclusions or recommendations, a spokesman for the department said.
After the final report from the Healthcare Commission was published on 9 October, Health Secretary Alan Johnson suspended the apparently generous severance pay offered to the trust's chief executive Rose Gibb, who resigned just days before the findings were made public.
Last week he also accepted the resignation of the chairman, James Lee.
"Since the failings of leadership at the trust were such as to require you to accept the chairman's resignation on 14th October, what had you done, months before, to address the significant failings of the trust?" Mr Lansley wrote in an open letter to the health secretary.
"Why has action by ministers and the department have to wait until the public outcry?"
Staying in bed
The Healthcare Commission concluded that as many as 90 people had died between 2004 and 2006 in two separate outbreaks of C. difficile, and that the poor handling of the infection had probably contributed to the deaths of dozens more.
It found a litany of problems, including a shortage of nurses so dire that staff did not have the time to wash their hands between patients and on some occasions even told those in their care to "go in their beds".
The board itself was obsessed with meeting targets, both in terms of finance and treatment, and this sometimes meant that wards were very overcrowded.
In the wake of the report, the Liberal Democrats started their own investigation into bed occupancy levels, finding that over half of trusts had rates above 85%.
This, they said, was contributing to hospital infections such as C. difficile and MRSA, and was a particular problem in geriatric wards, as bugs "spread more quickly between elderly patients".
"As long as this situation continues, it will undermine efforts to successfully combat hospital acquired infections," said health spokesman Norman Lamb.
"It puts staff under undue pressure and risks corners being cut in order to get new arrivals admitted on time."
But experts said the relationship between bed occupancy and infection was more complex than some assumed.
"In rehab wards for instance, where patients are staying for long periods of time, the turnover rate is low so the issue of cleaning beds between patients is not so pressing," said Nigel Edwards, director of policy for the NHS confederation.
"It is more of a problem where you've got people coming in an out all the time, but the bottom line is that you cannot draw a clear link between infection and occupancy."