Deborah Glass, IPCC Deputy Chair, said: "It is one year since the Hillsborough Independent Panel issued its report. That report was the result of the resolve and determination of the Hillsborough families. It resulted a month later in my announcement of the biggest criminal and police misconduct investigation in the history of England and Wales, the quashing of the original inquest verdicts and the appointment of Jon Stoddart to lead the manslaughter investigation in December 2012, and the appointment of a Coroner in February 2013.
"One year on from the publication of the Panel report it is worth reflecting on the progress so far.
"We have set up and begun an investigation on a scale not previously seen before. Our work has established the foundations for the investigation being conducted by Jon Stoddart's team and the inquest process.
"This has included recovering a huge amount of documentation – both that seen by the Panel and new material not previously seen – acquiring and fitting out a building with the right IT and security, recruiting staff and building the biggest HOLMES database server in Europe.
"Those are significant achievements in themselves. However alongside the set-up work we have also been getting on with the job of investigating the aftermath of the disaster.
"From our work on this we have recovered West Midlands policy books that have never been seen by previous inquiries. We have identified the statements of 74 more officers which may have been amended. We have also uncovered material which would suggest that fans' witness accounts may have been altered. We have recovered pocket notebooks from officers who were on duty on the day of the match. We are in the process of interviewing all the surviving officers whose accounts were amended.
"We are also about to issue an appeal for witnesses. This appeal, which will be launched next week, forms a crucial element to our investigation into how West Midlands Police conducted its enquiries into the disaster. We want to hear people's experiences of that process. We have already had a number of people contact us with concerns that their statements were amended and we have no doubt there are others who have not contacted us: we want to be able to present as full as possible a picture of witness evidence both for the inquests and the criminal investigations.
"I cannot emphasise enough the significance of all this work. It builds on the work of the Hillsborough Independent Panel. But their work was a starting base. I acknowledge and understand the views of those who want quicker progress, and I cannot ask those who have waited 24 years to be patient. But I would ask them to speak to us to understand the complexity of the investigation we are conducting and the progress we are making; see for themselves the dedication and professionalism of our staff; and to continue to assist us in our work.
"This is an ongoing criminal investigation the like of which has never been seen before in this country. Already we are uncovering more about the disaster and its aftermath. Hillsborough has had a history of inquiries by the police and others, many completed quickly, coming to flawed conclusions. Our investigations need to deliver the last, definitive account.”