Secret intelligence material relating to the murder of LVF chief Billy Wright may be suppressed or withheld, the inquiry into his death heard yesterday.
Inquiry chairman Lord MacLean accused the PSNI of delaying the inquiry by holding back intelligence - and gave police one month to produce it.
A special hearing in Banbridge was also told that the Ministry of Defence is seeking a ministerial gagging order to suppress other sensitive information.
Lord MacLean said "significant gaps" remain in the thousands of documents provided by the PSNI.
"In particular, the outstanding gaps are in the intelligence information that we think exists and is not being produced," he said.
The inquiry also heard that the Ministry of Defence is seeking a restriction notice to suppress material which the panel "considers central to one part of the investigation".
Lord MacLean said this was a "crucial development in the inquiry which may have far-reaching consequences".
He indicated the MoD has provided the material in question but now wants a Government minister to order the inquiry to withhold that material from any of its public deliberations.
The MoD's bid for the gag has contributed to the delay in the inquiry's hearings, but Lord MacLean said " the most significant reason" was the PSNI's handling of documents.
The inquiry had been due to resume on September 10, but has been postponed because of problems with evidence.
David Wright, the father of the LVF chief murdered inside the Maze in 1997, denounced the PSNI as "not fit for purpose" over the ongoing problems with material. The police were first given 30 days to produce documents in November 2005.
After several delays, Lord MacLean said the PSNI indicated in May this year that it had produced all the documents requested by the inquiry and " that the PSNI considered the matter was closed".
But he revealed that the PSNI has since set up a review under former Assistant Chief Constable Sam Kincaid - who was in charge of PSNI dealings with the inquiries before he retired - to reconsider whether the Wright inquiry had received all relevant material. Lord MacLean said new documents, " including intelligence material", would be provided next month, according to the PSNI.