The families of the Manchester bombing victims have called for more "openness and transparency" from police about the ongoing criminal investigation.
Most of the updates families had received "had come from the press", a lawyer told a pre-inquest hearing at Manchester Town Hall.
Steve Howe, whose wife Alison died in the attack walked out of the court, and said the delays have been frustrating.
During the two-hour hearing the families were told inquests will not be held until at the earliest April 2020 - almost three years after the attack on May 22 2017.
Progress on holding the inquests has stalled as they cannot be held before the conclusion of any criminal investigation and trial of suspects.
But the hearing was told the investigation is still "live" and the UK has since November 2017 been trying to extradite the bomber's brother, Hashem Abedi, from custody in Libya.
Lawyers for the police and the inquest warned that making information public could lead to prejudicing a jury and preventing any future fair trial.
Mr Weatherby said the information sought included questions about what has been achieved so far, what hurdles remain in returning Hashem Abedi to the UK, whether he is in detention in Libya, and who he is being held by.
Jeremy Johnson QC, representing GMP, said the force was "very sympathetic" to the families' request, but progress was not being driven by the police as other authorities in the UK and Libya were also involved.
He said officers will meet the CPS to try to give more information to the families and answer their questions.
In opening remarks to the hearing, coroner Sir John Saunders said it was a matter for the CPS and GMP to decide how much information could be made public without risking a fair trial.
He also said he had to balance the needs of involving the families in the inquest and having an open hearing with the issue of sensitive material from the security services being made public.
Only people with a certain level of security clearance can view some of the evidence and that issue may also affect whether the inquest can be held before a jury.
The inquest will also include a "most vigorous" investigation into whether the attack could have been prevented, the background and radicalisation of Abedi, and the information held and actions by the police and security services.
It will also cover the build-up and the attack itself, security arrangements at the arena, the emergency response, the victims and their cause of death, and whether any deaths could have been prevented.
Another pre-inquest hearing will be held later in the year.