The Health Secretary has visited Stafford Hospital, less than 24 hours after the government said there would be a full public inquiry into it.
The Conservatives had promised the probe in opposition after the hospital was criticised for its "appalling" standards which caused needless deaths.
Andrew Lansley said he visited some areas that were most criticised in the original Healthcare Commission report.
He said there had been "a substantial improvement".
Mr Lansley visited the accident and emergency department and two wards which were particularly criticised.
Mr Lansley said: "From my point of view it was very important to hear direct from the new leadership on those departments about how they are changing things.
"[It was very important to hear] how they're providing additional staff, what those staffing levels are enabling them to do to make patients feel safe and [get] good quality care."
Campaigners consistently said a full public inquiry was the only way to uncover the failings, but previous ministers had resisted.
In March 2009 the Healthcare Commission reported there had been at least 400 more deaths than expected between 2005 and 2008.
It cited a catalogue of poor standards, including cases where receptionists had been used to assess emergency patients.
An independent inquiry launched by the government was held in private and reported in February, saying the trust had become driven by targets and cost-cutting.