The judge leading the Leveson Inquiry into media standards has suggested that the planned second part of his probe - into specific allegations of wrongdoing at the News of the World - may not go ahead.
The lengthy delay caused by the need to await the conclusion of police investigations and possible trials means that it will be "very many months, if not longer" before the second part of the inquiry can begin, said Lord Justice Leveson.
Although he did not rule out pressing ahead as planned, he suggested that consideration should be given to the value of a second inquiry which would involve "enormous cost" to taxpayers and participants and would "trawl over" material which is many years out of date.
In a ruling published late yesterday on the inquiry website, Lord Justice Leveson said he believed it was "in everyone's interests" to allow the first part of his investigation - currently taking evidence at the Royal Courts of Justice - to go "as far as it possibly can" in the hope of answering public concerns about press behaviour.
When Prime Minister David Cameron commissioned the probe in the wake of revelations about phone-hacking at the News of the World in July 2011, he gave Lord Justice Leveson a remit to carry out an inquiry in two parts.
The first, to start immediately, would inquire into the "culture, practices, and ethics" of the media, including contacts and relationships between the press, politicians and police, and make recommendations for a more effective policy and regulatory regime in the future.
Only after the completion of any police investigations or trials would the judge begin the second part of the inquiry, addressing "the extent of unlawful or improper conduct within News International, other newspaper organisations and, as appropriate, other organisations within the media", as well as allegations of corrupt payments to police and complaints about the initial police response to phone-hacking claims.
With police currently investigating a number of individuals and no indication of whether or when any prosecutions may be brought, it is thought likely to be 18 months or longer before the second part of the inquiry can begin.
In his ruling, Lord Justice Leveson said: "The public concern which led to the setting up of this inquiry is beyond argument or debate.
"I do not know whether there will be prosecutions but, having regard to the number of arrests and the quantity of material seized - including the 300 million emails which it is said have had to be analysed - if there are, it is likely that the process of pre-trial disclosure and trial will be lengthy, so that Part 2 of this Inquiry will be delayed for very many months if not longer.
"In those circumstances, it seems to me that it is in everyone's interests that Part 1 goes as far as it possibly can.
"If the transparent way in which the inquiry has been conducted, the report and the response by Government and the press - along with a new acceptable regulatory regime - addresses the public concern, at the conclusion of any trial or trials, consideration can be given by everyone to the value to be gained from a further inquiry into Part 2.
"That inquiry will involve yet more enormous cost, both to the public purse and the participants.
"It will trawl over material then more years out of date and is likely to take longer than the present inquiry, which has not over-focused on individual conduct.
"Obviously, the more restrictive in its analysis that Part 1 has been, the greater will be the legitimate public demand for Part 2."
Lord Justice Leveson stressed that the possibility that the second part of the inquiry may not go ahead has not affected his approach to the first part.
But he added: "It is undeniably a sensible strategic consideration for those who have participated in this inquiry."
The potential for the inquiry to end without a full investigation of phone hacking at the News of the World raised concerns among campaigners.
Labour MP Chris Bryant, whose phone was hacked, told BBC Radio 4's World At One: "All I ever wanted ... was an inquiry into what went on at the News of the World and why the cover-up was allowed to continue for so many years - basically, why News of the World nearly got away with it.
"All the rest of the flummery about relationships between different elements of the media, and how they practice and so on, was not part of what we were demanding at all.
"That's my concern - that if we don't look at the specifics of what happened at the News of the World, the cover-up and so on, and if nobody finally adjudicates on that then we will have missed the real problem here."
Professor Brian Cathcart, from the Hacked Off campaign, told the programme: "If we were to just stop at the end of part one we would never address those issues of the detail, we would never get the clear picture, the total picture of what happened at the News of the World."