What's the question?

"This time, it's palpably nasty." That's Quentin Letts, the Mail's theatre critic. West End and Westminster.

It captures what everyone now feels about the long-running so-called 'phone hacking' scandal. For half a decade it has interested and outraged people like me - the sort of people Nick Robinson dismissed on Today as "professors of journalism ethics".

But now it's on everyone's mind. And lips: 'how could they sink so low?'

But reaching the tipping point is one thing. Where it falls is another.

On 6 July at the House of Lords, a campaign was launched to press for a public inquiry. (I should declare an interest: I was asked to lend my name to the campaign, partly because of earlier blogs I'd written on this website.)

Now is the chance for the public to tell journalists about the kind of press they want - a press they would trust.

It goes way beyond News International's serial offending - though that's the priority for now: discovering the number and nature of News of the World journalists' crimes, and those of the 'investigators' they hired.

But it's important that the investigation of this scandal doesn't end there.

We, the public, need to know how the culture of contempt - a culture of which phone-hacking is just the nastiest tip of a nasty iceberg - came to be the norm in all tabloid newsrooms. We need to know more about the routine of bribing bank and DVLA clerks, doctors' receptionists, nurses... anyone standing guard over private information. And bribing policemen - something News International's Chief Executive, Rebekah Brooks, boasted to MPs about.

We need to know, too, where the police were when this story broke five years ago. Why were those bin bags full of incriminating evidence stuffed away in a cupboard for half a decade? Did they think it was enough to catch the two crooks who'd hacked royal phones? Did they think phone-hacking as a matter of routine wasn't really very criminal at all? Or was there something more sinister at work? The symbiosis of the Met and News International?

We need to know more about the links, formal and informal, between political leaders and the Murdoch empire.

We need full disclosure about and proper, informed scrutiny of the kind of people who aspire to be at the helm of News International and BSkyB. Are they the kind of people the public want in charge of so much of the media?

And we need the Press Complaints Commission to tell us why it has spent the greater part of its two decades of life failing miserably to hold the press to account - even for the most disgusting breaches; not just of the risible Editors' Code but of any understanding of human decency.

We, the public, need to decide whether to call time on the running joke that has been press self-regulation. And whether we need something else in its place.

This matters. It matters because news isn't just a business like any other. And because the one thing that distinguishes journalism from rumour and gossip - trust - is in such short supply.

Tabloid publishers and editors may be content that eight out of ten readers don't believe a thing their newspaper tells them - but still buy them.

They may once have been persuaded that more intrusion, more bribery, more phone-hacking was the way to secure their future.

They can't any more. And the public doesn't have to accept it.