Saunders Law, a London-based legal firm, confirmed that hundreds from the Hillsborough Families Support Group are to pursue legal action for damages against the two forces after blame tried to be shifted on to the Liverpool fans.
The law firm, which is co-ordinating the action, said that families believe “justice will only be established through accountability”.
The lawyers were first instructed following the publication of the Hillsborough Independent Panel report in September 2012 which revealed at least 116 witness statements had been doctored to cast police in a favourable light against those who died.
The claims were issued last year but were forbidden from being published until the inquest had ended.
The law firm said: “The claims concern the cover-up and actions intended to wrongly blame the deceased and Liverpool Football Club supporters for the tragedy, for which there has still been no proper admission or apology.
“Despite a half-hearted admission after publication of the Hillsborough Independent Report, we now learn South Yorkshire Police spent an estimated £19m of taxpayers’ money on defending the indefensible at the inquest.”
It said abuse by the forces was on an “industrial scale”.
“In addition to the police wrongdoing that caused the deaths, there is evidence of the systematic cover-up intended to transfer the blame for what happened from South Yorkshire Police to the innocent, by spreading lies, doctoring evidence, pressurising witnesses, and suppressing the truth.
“The evidence points to abuse on an industrial scale by both South Yorkshire and West Midlands Police, beyond any ‘one bad apple’ analysis. In addition to actions by individuals, the evidence suggests institutional misfeasance by these bodies directed against our clients and the fans generally.”
Meanwhile, police officers who served South Yorkshire in the 1980s have been told they “did a good job” despite the Hillsborough disaster.
Rick Naylor, secretary of the South Yorkshire branch of the National Association of Retired Police Officers, said ex-officers acted with “dignity” despite the “bile and hatred” aimed at them.
In a message entitled “It was a bad day” and accidentally posted on a website for retired South Yorkshire Police officers, Naylor wrote: “After all that transpired yesterday it has not shaken my belief — I worked in a great police force with fantastic people who did extraordinary things.
“I am extremely proud to be an ex-South Yorkshire cop and I will hold my head up.
“South Yorkshire Police faced immense challenges in the 1980s — the steel strike, the miners’ dispute and Hillsborough, and along the way we caught the Yorkshire Ripper! You will be feeling sore, angry and disheartened and that is understandable but you did a good job — we all did!”