The UK’s police watchdog has claimed that fan statements given to officers after the 1989 Hillsborough disaster may have been altered.
New evidence regarding possible police conduct following the tragedy, in which 96 Liverpool fans died, has come to light during an investigation by the Independent Police Complaints Commission (IPCC).
The IPCC also said there was evidence that a further 74 police officers’ statements may have been amended -- in addition to the 164 already known about.
This new evidence has emerged after 90 police pocket books were recovered along with notebooks and other documents unearthed by South Yorkshire Police.
And the revelations have come a day before the first anniversary of the publication of an independent report exonerating fans of any blame for the deaths at an FA Cup semi-final between Liverpool and Nottingham Forest in Sheffield.
The Hillsborough Independent Panel’s report highlighted the extent to which the police and emergency services attempted to cover up their culpability in the tragedy, in which supporters were crushed to death on an over-populated section of terracing.
Of the 164 police statements known so far to have been altered, 116 had negative comments about the policing of the match between Liverpool and Forest changed.
Margaret Aspinall, chair of the Hillsborough Family Support Group, said that campaigners had long believed that fan statements had been altered.
She said: "This doesn't surprise me. We thought it happened -- now it is in black and white."
The IPCC is examining police conduct in the aftermath of the Hillsborough disaster.
It is also looking at how West Midlands Police investigated South Yorkshire Police's conduct for the original inquiry, led by Lord Chief Justice Taylor, which published its report in January 1990.
It was announced last month that the watchdog was looking for police notebooks after it emerged that one officer wrote notes on the day of the tragedy, despite being told not to by commanding officers.
IPCC deputy chair Deborah Glass said that an appeal for witnesses would be launched next week, as part of an investigation into the way the initial inquiry was handled by the West Midlands force.
She said: "We want to hear people's experiences of that process. We have already had a number of people contact us with concerns that their statements were amended and we have no doubt there are others who have not contacted us.
"We have recovered West Midlands policy books that have never been seen by previous inquiries.
"We have recovered pocket notebooks from officers who were on duty on the day of the match. We are in the process of interviewing all the surviving officers whose accounts were amended."
A second investigation, focusing on possible criminal behaviour by any people or bodies with responsibility for fan safety at Hillsborough, is being headed up by former Durham chief constable Jon Stoddart.
Fresh inquests into the deaths of the Hillsborough victims will begin on March 31 next year, at a venue in the North West of England to be confirmed.
The original inquest verdicts of accidental death were quashed in December.
Campaigners have long maintained that those original verdicts prevented a proper investigation into the role the police and emergency services played in the tragedy.