Bereaved families have blasted a "secretive" inquiry into a Staffordshire hospital with "appalling" standards of care.
Members of Cure The NHS protested outside the Department of Health in central London where they waved banners calling for the resignation of Health Secretary Andy Burnham.
The inquiry was launched into events at Stafford Hospital after a Healthcare Commission investigation found a catalogue of failings at Mid Staffordshire NHS Foundation Trust, which also runs Cannock Chase Hospital, put hundreds of patients' lives at risk.
The commission found between 400 and 1,200 more people died than would have been expected in a three-year period from 2005 to 2008.
Cure The NHS believes the independent two-month inquiry has gone over the same ground as the Healthcare Commission report and will not offer anything new.
Campaign group founder Julie Bailey said she was angry that inquiry chairman Robert Francis QC, who is due to hand in the report, ruled last year that the probe should be held in private.
The campaign group renewed calls for a full public inquiry as they handed in a blank piece of paper to Mr Burnham's personal assistant.
Ms Bailey said the paper represented the fact that the group was not even allowed to see evidence from the inquiry gathered by its own lawyers. She said the lawyers were allowed to sit in as hospital staff gave evidence but had to sign a confidentiality agreement, meaning they could not share the evidence with their own clients.
Ms Bailey said: "We've known right from the start that this inquiry would be a whitewash to protect the Government and so it has proved. We remain convinced that the only way to get to the full truth about the disaster at Stafford Hospital will be through a full public inquiry under the 2005 Inquiries Act with witnesses compelled to attend and be cross-examined under oath.
"Cure The NHS urges Mr Burnham to produce the report in full, with all of the evidence, as soon as possible. All bereaved relatives and the public have a right to see it." She cited "staff shortages" and "appalling" management for the disaster and added: "We also find it unforgivable that not one of them has been held to account for what happened and the hundreds of lives lost."
The Observer reported at the weekend that the inquiry report will conclude the trust actively discouraged staff from expressing fears about the safety of patients. The newspaper reported that senior managers will be accused of promoting a culture of secrecy.
When the inquiry opened in November, the foundation trust reiterated its apologies to patients and their families.
In its opening statement to the inquiry, the trust said it wished to once again sincerely apologise for "harm and distress" caused to patients, their families and loved ones at Stafford Hospital.
