A probe into the police handling of the shooting of a Brazilian man in London may not be ready until late summer.
Sir Ian Blair has faced criticism over his management
Relatives of Jean Charles de Menezes have learned the "Stockwell 2" report cannot be finalised until Metropolitan Police chief Sir Ian Blair is quizzed.
Sir Ian and another senior police figure are said to be unavailable until late July or August.
The family of Mr Menezes, who was shot in 2005, said the delay "added insult to injury".
The inquiry centres on the aftermath of the shooting of Mr Menezes, who was mistaken for a suicide bomber.
The "Stockwell 2" inquiry into the 22 July shooting at Stockwell Tube station in south London, is being handled by the Independent Police Complaints Commission.
The news of the investigation's delay comes as a pre-inquest review is held at Southwark Coroner's Court.
It is examining the progress of the original inquiry into the actual shooting which could determine if any criminal charges are to be brought against police.
A spokesman for the victim's family said it was an "outrage" that neither investigation had been finished.
"This adds further insult to injury to the family as they approach the one-year anniversary of Jean's murder," the spokesman said.
"We believe it is a disgraceful situation where the head of the Metropolitan Police... cannot find time for almost two months to report to the IPCC.
"The IPCC need to exert their authority now in order to have any further credibility."
An IPCC spokesman confirmed that the Stockwell 2 inquiry would be delayed but said the police was "co-operating with their inquiries".
"The investigation is complex and is taking longer than we expected for a number of reasons," the spokesman said.
"The timing of any outstanding interviews is not a major factor or a matter of disagreement between us and the Metropolitan Police Service."