Families bereaved by the Hillsborough tragedy have learned that they will get access to secret police and government documents within three months after a long campaign for the papers to be released.

The Hillsborough Independent Panel has analysed more than 400,000 pages of documents from 80 organisations concerning the disaster, in which 96 Liverpool fans were crushed to death on overcrowded terraces at the Sheffield Wednesday ground during the FA cup semi-final in April 1989. It will hand them over on 12 September – more than 23 years after the tragedy.

An official inquiry found that the main cause of the fans' deaths was a failure by South Yorkshire police to control the crowd.

In a statement released on Wednesday, the panel said the documents would be disclosed to the families first, and it hoped that "by making this announcement today it will give the bereaved families sufficient time to prepare for the disclosure". It emphasised that one of the panel's central objectives had been consultation with the bereaved families.

The home secretary, Theresa May, said in a written statement: "The government is fully supportive of the work of the independent panel chaired by the Bishop of Liverpool. The panel's work has been detailed and complex, but the government is pleased that it will complete its work by the autumn."

Precisely how the files will be released is still being discussed by the independent panel set up by the Home Office to oversee the disclosure. But it is understood that the relatives of the Hillsborough victims will be given access to the material before the documents are released to the public later that day.

Margaret Aspinall, chairwoman of the Hillsborough Family Support Group, said it was "great news" that families, survivors and fans had a date everybody could work towards. Aspinall, whose 18-year-old son James died at Hillsborough, said: "September 12 will undoubtedly be an emotional day for all the families."

Sheila Coleman, spokeswoman for the Hillsborough Justice Campaign, said: "We always knew this date would soon be announced. It's a shame the full cabinet minutes are yet to be released after they were leaked and the result of the inquiry into how the leak occurred."

The Cabinet Office is carrying out an inquiry after some documents were leaked to the BBC earlier this year.

The most controversial element of the papers seen by the corporation was a briefing note to the prime minister at the time, Margaret Thatcher, days after the disaster. In the note, an unnamed senior police officer wrongly blamed drunken Liverpool fans for the disaster.

Lord Justice Taylor's official report into the disaster, in 1990, said the "great majority [of supporters] were not drunk or even the worse for drink", and that "some officers, seeking to rationalise their loss of control, overestimated the drunkenness in the crowd".