For months, there have been a series of high court hearings about the extraordinary behaviour of editors, journalists and managers who once worked for Mirror Group Newspapers (MGN). Yet the disturbing revelations, which involve allegations about the wholesale interception of voicemail messages by three MGN titles, appear to have passed under the mainstream media radar.

It’s as if phone hacking is yesterday’s story and no one cares any longer to know the truth. Neither newspapers nor broadcasters are giving the matter anything like the kind of attention they once devoted to similar intrusions into privacy by the News of the World (NoW), which led ultimately to that paper’s closure.

But it is time to break the silence. What journalists at the Daily Mirror, Sunday Mirror and the Sunday People did in the early years of this century requires proper public scrutiny.

Just as important, arguably more important, is the need to discover why their grubby activities escaped censure and what the MGN board, its legal team and senior managers did, and didn’t know or do, at the time.

A quick bit of history.

It was 2006 when the public first learned about hacking by the NoW when the paper’s royal editor and a freelance “private investigator” were arrested. Three years later, the Guardian’s Nick Davies revealed that many hundreds of celebrities had had their phones hacked by the paper.

His dogged investigation finally caught the public imagination in 2011 when he told how NoW journalists had hacked into the mobile phone of 13-year-old Milly Dowler, after she had been abducted and subsequently murdered in 2002. At the time, the NoW’s publisher, Rupert Murdoch, was identified as the villain of the piece for running a company – then trading as News International – which had allowed staff to use illegal and unethical methods to obtain stories.

Plenty of journalists, however, were sure that hacking had not been confined to the NoW.

I was among those who received information that similar practices had been carried out by MGN staff. Nor was I alone in raising the allegations in public and asking for comments from the management.

The then chief executive, Sly Bailey, asked me for evidence. I replied by suggesting it was she who had the power, and the duty, to hold an internal inquiry. I said the same to the company’s secretary and legal director, Paul Vickers. He too said there was no proof of hacking.

Then BBC2’s Newsnight ran a segment in which it reported on “routine phone hacking in the newsroom” of the Sunday Mirror.

I approached Bailey and Vickers once again to ask what they thought of the Newsnight report. I was not alone. Several of the company’s big shareholders also asked.

They responded by ordering what was euphemistically called “a review of Trinity Mirror’s editorial controls and procedures”.

Why does Reach fight on? It has already cost it more than £75m to deal with the hacking claims

Vickers made it clear that it would not amount to an investigation of past activities by its journalists. It was, instead, a comic exercise in corporate face-saving, as was made clear in his evidence to Leveson.

He explained that he had written to his group’s “senior editorial executives” to ask whether they had any knowledge about any of their staff having intercepted phone messages. He said: “All 44 letters were returned to me signed with no issues raised.” How did he keep a straight face?

When Bailey appeared at the Leveson inquiry, which was set up to consider the culture, practices and ethics of the press, she was questioned about the swirl of MGN hacking rumours. Asked about the claims, she said there was “no reason to investigate ... unsubstantiated rumours”, adding “I have seen no evidence that phone hacking has ever taken place at Trinity Mirror.”

No evidence existed because no editor had been put under pressure.None of the specific allegations had been put to journalists. None of the staff had been asked to come forward to give confidential statements. No internal emails had been monitored. It was the very definition of a whitewash.

The following year, MGN received its first tranche of civil claims by people complaining about being hacked. They included the former England football manager, Sven-Göran Eriksson, former footballer Garry Flitcroft, actor Shobna Gulati and Abbie Gibson, the former nanny to David and Victoria Beckham’s children. All have since settled.

At the latest count, 71 claimants are now engaged in legal action against MGN. Not that many people seem to know that.

It is doubtful if they know that in January, Mr Justice Mann, a high court judge, spoke of allegations that MGN editors instructed private investigators to obtain information about Milly Dowler as “serious and inflammatory”.

He was responding to a statement by the barrister, David Sherborne, who is leading a legal team representing the claimants who had spoken of “widespread serious misconduct” by the three Mirror group papers.

Similarly, it is doubtful if too many people know that this month, also in the high court, MGN’s lawyers sought to limit the way in which the alleged hacking victims are hoping to present their case. The claimants are particularly concerned to know whether MGN’s legal department had been aware of hacking. Mr Justice Mann, in refusing to strike out claims about the legal department’s knowledge, or lack of it, ruled that they could be aired in court at a future hearing.

I am not unsympathetic to the plight of Reach, the company which now runs the MGN titles. The old managers went long ago. Few, if any, of the journalists who were around in the years immediately after 2000, when hacking is alleged to have been rife at the titles, now works for the company.

But why does Reach fight on? It has already cost the company more than £75m to deal with the hacking claims, including settlements. Why does it not settle with claimants and tell them – indeed, tell all of us – what happened and who was responsible? Many of us know there is a big story to tell about hacking by Mirror group editors and journalists, as big as that which swept the News of the World into the dustbin of history. It is time, surely, for the publisher to come clean.