The Independent Police Complaints Commission (IPCC) has been given new powers to compel police officers and staff to testify as witnesses as it prepares for an extensive investigation into the Hillsborough coverup.

The home secretary, Theresa May, announced the two new powers in a written statement on Thursday, which revealed that the police watchdog expected to start interviewing witnesses early next year in its inquiry into alleged wrongdoing by officers following the 1989 football disaster. May said the families of the Hillsborough victims had already waited 23 years.

The fast-tracked changes, which will be contained in a police complaints and conduct bill, will be controversial because some in policing disagree with officers having fewer rights than civilians in being compelled to attend interviews, albeit as witnesses. The powers carry no sanction if ignored, but Ggovernmentofficials said existing police procedures would allow for the disciplining of any officer ignoring a request for interview. It would not stop no-comment interviews or officers reading from prepared statements.

May said the first new power would "compel individuals currently serving with the police or certain other policing bodies, to attend an interview in relation to any investigation managed or undertaken by the IPCC in the capacity of a witness". The second new power would allow the IPCC to conduct investigations into allegations examined by its predecessor, the Police Complaints Authority in "exceptional circumstances".

The measures came about after talks with Labour. Yvette Cooper, the shadow home secretary, has called for the IPCC to be replaced by a new body with tougher powers. She said IPCC resources should be buttressed with help from other organisations to investigate Hillsborough: "I do believe that these investigations could be pulled together under a senior lead investigator able to co-ordinate across them and call on the resources of the IPCC but also the National Crime Agency and the home office if necessary."

The Hillsborough Independent Panel's report exposed the scale of the coverup by South Yorkshire police in the aftermath of the disaster in 1989 that left 96 people dead.

The panel found that officers altered 116 of their 164 statements to remove or amend comments that were unfavourable to South Yorkshire police, as they tried to blame the victims, the Liverpool fans, for the disaster.

The director of public prosecutions, Keir Starmer, is also examining if any possible crimes were committed by police.

The IPCC has told MPs that the total number of officers it may have to examine is 2,444, and its investigators will have to locate and comb through 450,000 pages of documents.