A criminal investigation into the police handling of the 1989 Hillsborough football disaster must happen, an ex-chief constable has said.
Richard Wells, who led South Yorkshire Police from 1990 to 1998, said charges were "absolutely essential" after a damning report into the tragedy.
It found police changed statements and tried to blame fans for a crush which led to 96 Liverpool fans dying.
Victims' families and politicians have called for urgent action on the report.
The current chief constable of South Yorkshire David Crompton said if the law was broken, there should be charges.
The report also found that 41 of the 96 who died had the "potential to survive" and calls have been made for fresh inquests.
The original inquests into the deaths in 1990 and 1991 recorded verdicts of accidental death.
'Failure of the state'
David Cameron said Attorney General Dominic Grieve would review the report as quickly as possible in order to decide whether to apply to the High Court to order new hearings.
Trevor Hicks, whose two daughters died in the disaster, said he wanted to see new "proper, fair and honest inquests".
The 96 Liverpool fans died after a crush on overcrowded terraces at Sheffield Wednesday's ground during the FA Cup semi-final between Liverpool and Nottingham Forest in April 1989.
Following the publication of the Hillsborough Independent Panel's report, David Cameron apologised to victims' families for the "double injustice".
He said they had suffered both in the "failure of the state to protect their loved ones and the indefensible wait to get to the truth", and in the efforts to denigrate the deceased and suggest that they were "somehow at fault for their own deaths".
Mr Wells said police forces across Britain had "a culture of authoritarianism, defensiveness [and] excessive secrecy" at the time of the disaster.
He said he had "swallowed, to my great regret now, the prevailing account - that the statements had been looked at for criminal justice purposes and emotional, non-evidential material had been removed".
Mr Crompton said: "My position is a very simple and straightforward one, which is that if people have broken the law then they should be prosecuted.
"It doesn't make any difference whether they're a police officer or anybody else."
The current chief constable of West Yorkshire, Sir Norman Bettison, was a serving officer in the South Yorkshire force at the time of the disaster.
He said he welcomed "the disclosure of all the facts that can be known because I have absolutely nothing to hide".
'Need for accountability'
The families have always challenged the original inquest, which concluded all the victims had been dead or brain dead 15 minutes after the game kicked off at 15:00.
By analysing post-mortem test results, the panel found 28 of the 96 victims had no "obstruction of blood circulation" and there was "separate evidence that, in 31, the heart and lungs had continued to function after the crush".
The medical advisor on the panel, Dr Bill Kirkup, said up to 41 of the 96 who died could have potentially been saved if they had received treatment earlier.
Margaret Aspinall, chairwoman of the Hillsborough Families Support Group, said: "I'm very grateful that the fans and the supporters have been exonerated as well as our dead, but most importantly we need accountability for the 96," she said.
"We've got to demand that these verdicts are overturned."
Lord Falconer, a former lord chancellor and justice secretary who has been advising the Hillsborough families on legal issues, said how long it took to set up a new inquest "very much depends upon whether organisations such as the South Yorkshire Police accept that there needs to be [one] and accept their culpability in relation to it".
"The more the state organisations accept fault and open completely their books to proper examination, the quicker everything can happen," he said.
Other reactions from senior figures and families to the report have included:
- Joan Hope, whose son John McBrien died in the tragedy, who said she was "disappointed because I was hoping for a statement saying the police were guilty"
- Ex-Home Secretary Jack Straw, who said Margaret Thatcher's government created a "culture of impunity" in the police that led to the Hillsborough cover-up
- Sir Norman Bettison, the current chief constable of West Yorkshire who was a senior officer in South Yorkshire Police's Hillsborough operation, who said he had "absolutely nothing to hide"
- Shadow home secretary Yvette Cooper, who called for an Independent Police Complaints Commission criminal investigation into the conduct of officers
- Nick Clegg, who also called for a criminal inquiry, adding: "I am reeling with horror at the revelations - despicable things happened. The wheels of justice must now turn but it seems to me there was criminal activity and police must pursue this"
- West Midlands Police Assistant Chief Constable Gareth Cann, who said the force was to "consider and review the content of the Independent Panel's report" which said that it knew South Yorkshire officers altered statements
- Football Association chairman Sir David Bernstein, who said the tragedy "should never have happened. Nobody should lose their lives when setting out to attend a football match and it is a matter of extreme regret and sadness that it has taken so long for these findings to be published and the truth to be told"
- The Sun's editor Dominic Mohan, who said the newspaper was "deeply ashamed and profoundly sorry" for the headline The Truth on the front-page story which ran four days after the disaster
- The Mayor of London Boris Johnson, who apologised for an article he wrote in 2004 in which he said Liverpool fans were partly to blame for the Hillsborough disaster
The Hillsborough panel's report found police and emergency services had made "strenuous attempts" to deflect the blame for the disaster on to fans and that 116 of the police statements identified for "substantive amendment" had been "amended to remove or alter comments unfavourable to South Yorkshire Police".
Liverpool fans and relatives of the victims have campaigned for 23 years to find out exactly what happened on the day of the disaster.
'In good faith'
An independent inquiry led by Lord Chief Justice Taylor in the immediate aftermath of the disaster found the main cause had been a failure in crowd control by South Yorkshire Police.
In 1997, the then Home Secretary Jack Straw ordered Lord Justice Stuart-Smith to review "new" evidence which had not been submitted to the inquiry and also dozens of police and witness statements, which had been altered.
Lord Justice Stuart-Smith concluded the evidence did not add anything significant and while statements should not have been edited, this was simply an "error of judgement".
Mr Straw said Lord Justice Stuart-Smith had "operated in good faith and I greatly regret that he could not get to the bottom of this".
"I regret that I had not spotted this - if I could turn the clock back, I would do so and some years of heartache for these families would have been saved."