According to News International the latest allegations in the phone hacking affair, made by Nick Davies in the Guardian and Labour MP Tom Watson in the Commons are “wholly inaccurate”. For four years the company told us much the same thing about similar allegations relating to private investigator Glenn Mulcaire, and it was wrong — so wrong that it is now ready to pay out compensation running into millions, while a police investigation is under way involving 45 officers. On balance, I know who I am inclined to believe.

The allegations double the scale of the scandal, and more. This is a second private investigator — Jonathan Rees — a second cache of documents, a second roll-call of victims (the Duchess of Cambridge, Tony Blair, Jack Straw…) and, though it may also include phone hacking, it clearly also includes a different modus operandi. It is clear, too, that the materials seized from and assembled about Rees in the course of a murder investigation (which resulted in charges against Rees that were later dismissed in court) are much more extensive. In the case of Mulcaire, the convicted hacker, two or three bin bags of material have yielded most of the information about his activities; the Rees materials are said to fill hundreds of boxes. The allegations also stretch back further in time, into the 1990s.

Watson says he has a letter from Sue Akers, the officer in charge of investigating the Mulcaire-News of the World affair, suggesting that the Rees case is outside her remit. Whatever else he got from the Prime Minister yesterday, Watson seems to have secured a statement that there is no limit to Akers’s remit and she can look at what she likes, if the information leads her there. (And by the way, why did Cameron look so angry and fed up about saying that?)

There are no grounds for believing News International denials. We have no evidence that they have investigated the matter themselves, and even if they made that claim their credibility would be wafer-thin since they have a record of boasting about thorough investigations which turn out (by their own admission) to have been nothing of the kind. The only appropriate response would have been to say (if that is really the case) that News International were unaware of the evidence behind the Watson and Davies allegations and that they would welcome a police investigation to clear things up.

But News International is now in a desperate position. It has no credibility left in this matter. Its senior executives, notably Rebekah Brooks but also for his past role James Murdoch, are hopelessly compromised. As its response to the Mulcaire events has shown, its only recourse is money, of which it has plenty — all it can do is pay people to go away and shut up, as it has been feverishly trying to do since 2008. This is a shameful position for the dominant media company in this country.

The Times, stablemate of the News of the World, didn’t even mention the new allegations in its print edition this morning. Who made that decision? Was it Brooks, the compromised chief executive and dead woman walking in this affair? On what grounds? To protect herself? To protect Rupert Murdoch? Certainly not to protect the Times, whose reputation has been sullied disastrously by all of this.

Before the new allegations the senior management of News International was in serious trouble, and in need of more than window-dressing and cheque-writing to redeem itself. Now it is surely in free-fall. In any other company, shareholders, employees and directors, not to mention customers, would be demanding wholesale change and reform. In this company only Rupert Murdoch matters. When will he acknowledge the scale of the disaster?

Brian Cathcart teaches journalism at Kingston University London and tweets at @BrianCathcart