Three Police Ombudman reports into historic killings in Northern Ireland will not be published pending the Loughinisland legal challenge, the office said.
Dozens of murders are covered by probes where collusion between the security forces and paramilitaries is suspected, including a loyalist mass shooting at a bookmaker on Belfast's Ormeau Road in 1992.
The delay was prompted by legal wrangling surrounding the Loughinisland murders in which six Catholic men were shot dead at the Heights Bar during an Ireland World Cup football match in June 1994.
An Ombudsman official wrote: "In the meantime investigations are continuing as before.
"However, any investigation which had been finalised and was awaiting the publication of a public statement will... unfortunately have to await the outcome of the current litigation."
She recognised the news would disappoint relatives whose loved ones were killed.
"It is important for the office to have clarity around its powers, particularly where they result in a public statement."
The independent Ombudsman Dr Michael Maguire investigates historic or current police conduct.
Retired police officers took a judicial review of Dr Maguire's conclusion that some officers colluded with gunmen at Loughinisland.
A new judge has been asked to hear another judicial review after a previous ruling that the Ombudsman's collusion finding was "unsustainable" and threatened to quash the report.
Cases affected by the decision to delay publication include:
- The murder of Damien Walsh at the Dairy-farm Centre in Twinbrook in West Belfast;
- An investigation into a series of murders in south Belfast including the killing of five people in Sean Graham's bookmakers in a loyalist gun attack on the Lower Ormeau Road;
- An examination surrounding 19 murders and three attempted murders in the south Londonderry and North Antrim areas throughout the early to mid-1990s.
Relatives for Justice caseworker Paul Butler has been supporting families engaging with the Police Ombudsman, including the family of Mr Walsh.
He said: "This is yet another blow to families.
"The Walsh family lodged their complaint 14 years ago during Nuala O'Loan's tenure as Police Ombudsman and understandably they are frustrated and deeply disappointed.
"Roadblock after roadblock has been placed in the way of the Ombudsman from funding cuts, to the Ombudsman having to resort to judicial action against the Police Service of Northern Ireland (PSNI) to obtain intelligence on these and other killings, and now this latest legal challenge taken by among others a former head of Special Branch that has had the result of postponing publication of completed reports."
He said families see these actions as a "concerted and strategic" rearguard effort by those with a vested interest in denying truth, accountability and ultimately justice.
The Ombudsman promised to keep the families informed as the situation develops in the weeks and months ahead.
"In the meantime, our investigations - both historical and contemporary - are unaffected and are continuing to be progressed."