The Independent Police Complaints Commission has rebuked the South Yorkshire police chief constable, David Crompton, for comments he made about the Hillsborough disaster in internal emails shortly before the Hillsborough Independent Panel published its report into the disaster on 12 September.

Crompton wrote to his deputy chief constable, Andy Holt, and Mark Thompson, the force's head of media, suggesting they prepare a series of facts, which "amounts to the case for the defence".

The email read: "One thing is certain – the Hillsborough Campaign for Justice will be doing their version … in fact their version of certain events has become 'the truth' even though it isn't!!"

The panel's report found conclusively that South Yorkshire police failures caused the disaster, in Sheffield Wednesday's football ground which had been unsafe for years. Afterwards, the panel found, the force mounted a concerted campaign, led by the former chief constable, Peter Wright, to shift the blame on to Liverpool supporters.

Professor Phil Scraton, who substantially authored the panel's report, said the email's contents were unacceptable.

The IPCC Commissioner, Nicholas Long, described the email as "at best ill-judged, and at worst offensive and upsetting".

Long said, however, the IPCC was taking no further action, and referred the issue to South Yorkshire's police and crime commissioner, Shaun Wright. He has already said he accepts Crompton's "regret for his language in this one particular email and his apology".