The Labour Leader Ed Miliband has called for what he calls a proper investigation into violent clashes between police and miners during the pit strike at Orgreave in South Yorkshire in 1984.
Mr Miliband's comments came during a speech to miners in his constituency. South Yorkshire police referred themselves to the Independent Police Complaints Commission in 2012 over allegations police officers had assaulted miners.
The IPCC says it is continuing with what it describes as a very complex process before deciding on future actions.
Police forces across the country have been asked to search their archives as part of the widening investigation into the Battle of Orgreave. The IPCC is considering launching a formal inquiry into the actions of South Yorkshire officers during the 1984 miners' strike.
Campaigners and former miners have been protesting outside the watchdog's Yorkshire office today as Matt Price reports.
The search for additional information forms part of the IPCC's brief to identify events from Orgreave which can still be investigated.
South Yorkshire Police documents are already being analysed. They are from an archive of 65 boxes thought to contain specific relevant information.
The remaining boxes are understood to contain general information about the miners' strike. However, the documents received do not cover the complete period under consideration but appear to be a snapshot of events.
As a result, the IPCC has widened its search for documentation to cover other police forces, in addition to legal representatives who represented miners in the court cases which followed the events at Orgreave.
The Independent Police Complaints Commission has asked all police forces in England and Wales to conduct searches of their archives to identify and provide any documentation they have relating to events at the Orgreave Coking Plant in 1984.
Campaigners calling for a public inquiry into the battle of Orgeave will protest outside the police watchdog offices in Yorkshire later. It's a year since the Independent Police Complaints Commission investigates police actions during the miners' strike.
A campaigning group, The Orgreave Truth and Justice Campaign, has been set up and they are demanding a public inquiry into the actions of the police at Orgreave Colliery during the miners strike in 1984.
South Yorkshire Police has already referred itself to the Police Complaints Commission over its involvement.