The Chief Constable of South Yorkshire Police has apologised for an "inappropriate and insensitive" internal email about the Hillsborough disaster.
David Crompton sent an email to colleagues in which he claimed a group representing the families of the victims of the football tragedy created an untrue version of events.
He also described the South Yorkshire force as becoming "roadkill" if it was not more innovative in its response to the Hillsborough Independent Panel report published last year.
The email was disclosed after a freedom of information request.
Mr Crompton said the email, sent to his assistant chief constable and head of press and communications, was not meant to cause offence.
He said: "The email from last September was written prior to the release of the Hillsborough Independent Panel report. It was never intended to cause any offence and I apologise if it has done so. Nor was it intended to challenge the integrity and views of those who lost loved ones in the Hillsborough disaster.
"Following the publication of the panel's report, I said in the most forthright terms that I supported the findings and that is still my position."
The email discussed how the force could use its website to respond to the findings of the panel. It said: "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!!
"I just have the feeling that the media 'machine' favours the families and not us, so we need to be a bit more innovative in our response to have a fighting chance otherwise we will just be roadkill."
Shaun Wright, police and crime commissioner for South Yorkshire, said he had informed the Independent Police Complaints Commission and the Home Secretary about the email. He said he was "disappointed" in the language used and had raised his concerns with Mr Crompton.