This is the week of the MacTaggart lecture: that ancient religious ritual which each August summons British television's scattered faithful to Edinburgh to talk shop, drink responsibly, and hear an assortment of fatwahs, imprecations and misty-eyed visions from that year's chosen prophet. This Friday it's the turn of Google's softly spoken but formidable Eric Schmidt. If it's a quietish Bank Holiday weekend or if Eric has something controversial to say, it could play big for a few days. If he says something momentous, it might have a life for decades.

But the truth is that good, bad or indifferent, most MacTaggarts are necessarily, indeed intentionally, of their moment and quickly fade. There is one recent exception, however: a MacTaggart which feels more telling today than on the day it was delivered; a MacTaggart which represents the high-water mark not just of one strain of economic and moral purism about media, but of the singular deference with which that purism was accepted for so long by so many, and that is James Murdoch's speech of 2009.

Subsequent events have given James's famous final flourish – that "the only reliable, durable and perpetual guarantor of independence is profit" – an unexpected and almost tragic irony. It's a phrase which sums up his entire case: that all forms of public intervention in and regulation of media are both morally reprehensible and practically useless, and that it is the market alone which can deliver brave, worthwhile, independent journalism. Yet it was under just these conditions – the lightest of light touch regulation, minimal oversight and accountability, commercial considerations to the fore – that the catastrophe at the News of the World unfolded.

But not everything that James Murdoch said that night in Edinburgh was wrong. While many of his shots still feel woefully off target, I believe he was right to ridicule the idea of newspapers being regulated and monitored in the same way as broadcasters. There is no good reason why privately owned and run papers should be held to the same content requirements or accountability as broadcasters who reach very large proportions of the public and who, in the case of the BBC, are paid for by everyone. Of course, that doesn't mean the current regulatory structures couldn't or shouldn't be reformed.

But it's vital that whatever recommendations emerge from the Leveson inquiry and the other investigations into the phone hacking scandal, they do not limit or have a chilling effect on the scope or dynamism of serious investigative reporting. Journalism which uncovers wrongdoing and which holds powerful interests to account is an important force for good. Indeed without it, very little of the phone-hacking scandal itself would have come to light. And sometimes, yes, editors will decide that their journalists can and should break rules, and even break the law, when an overwhelming public interest is at stake.

At the same time, the revelations at the News of the World demand that there should be a debate about the nature of "the public interest": how it should be defined and who should do the defining. How editors, regulators and courts should weigh up the question of proportionality, in other words of whether this practice would be justified in the context of uncovering that form of serious wrong-doing. Something which might be justifiable in the investigation of a major political scandal might feel wholly disproportionate in the pursuit of a celebrity who's alleged to be guilty of some minor personal misdemeanour.

At the BBC, I know of no instance of the practices at the heart of the News of the World story; nor indeed do we cover many of the kinds of stories in which these practices were used. We do however sometimes break the rules in what we take to be the public interest. For example, to demonstrate and subsequently prevent the serious abuse of vulnerable young people in a care home, we sent someone into the home posing as an assistant – something which is a breach of employment legislation. We believed that there was enough at stake to justify this action and we were pleased that, after the programme, it seems likely that the regulation and oversight of all care homes will be improved. But we also believe that there are boundaries: there has to be a balance between the gravity of the transgression and the public interest justification for the investigation. Where these problematic boundaries lie should also be part of the debate.

While it's vital that the space for serious investigative journalism is preserved, it's also true that our industry needs to grow up about standards, regulation and compliance. Journalists and programme-makers often debate these topics as if there were no middle ground between total, unconstrained freedom and totalitarian censorship.

If regulation can be streamlined and simplified, of course it should be – and at the BBC we will continue to review the additional controls we brought in after some of our own editorial problems. But those controls played an important part in helping us to restore public trust in the BBC to a level higher than before the problems occurred.

After the last batch of compliance reforms arrived at the BBC we were promised a paralyzing climate of fear – yet somehow that hasn't stopped the BBC doing more not less investigative journalism or getting higher marks from the British public for creativity and originality.

Underpinning any new measures in the light of the current scandal should be a determination across the industry to rediscover a journalism which is grounded in enduring values: honesty, fairness, decency. Whatever topic you touch on – the aftermath of the riots, the conduct of our politicians and other leaders, the way we bring up our young or treat our old – there is a palpable public hunger for a return, not just to a rhetoric about ethics, but to a practical, dependable, shared morality. On our airwaves and in the comment pages of our newspapers, we reflect this hunger almost every day in so far as it applies to other industries and walks of life. Can anyone seriously argue that it doesn't apply to the media industry as well?

The present crisis of values in media affected a newspaper (perhaps more than one newspaper) rather than a broadcaster or a new media player. But the rest of us shouldn't behave like holy-than-thou bystanders. In TV and radio, we've received our own series of humbling wake-up calls about values in recent years, first the wave of revelations about fake phone-ins and competitions across broadcasting then, with Celebrity Big Brother and The Russell Brand Show, with some ugly examples of abusive and bullying behaviour.

I believe that not just the BBC but the whole of the TV and radio industries have worked hard to learn the lessons from these episodes, but it would be a brave TV executive who said that he had nothing left to learn about editorial standards and practice or that he or she was certain that his own journalism was perfect in every regard. It is right therefore that the Leveson inquiry should take evidence from broadcast as well as print editors and journalists.

There are some, of course, who would love to shift the debate about events at the NoW away from these topics and instead towards other, less intricate and perhaps less uncomfortable issues – for example, the alleged dominance of the BBC, a cause for which James Murdoch is one of the principal advocates. One Sky lobbyist has even started to talk up legislative vengeance on the BBC because of its role in recent events. As Charles Lewington put it: "The communications bill next year will become a battleground for more arguments about media ownership and plurality of provision, and the BBC and others who fought the BSkyB takeover might come to regret stirring up a hornets' nest."

In fact the BBC today takes a smaller share of UK broadcast revenues than at any other time in its history. And it's a share that is all-but certainto fall over the coming years. Further, the BBC's new licence fee settlement means that there will be significant outright reductions to its scope. It's impossible to look at the facts and still argue that the BBC represents a growing threat of economic dominance in broadcasting. Needless to say, that doesn't mean that some people won't try. The case against the BBC for narrowing news plurality is, if anything, even less promising. In recent years, the number of TV news channels in this country has multiplied. Although newspapers fret about the BBC's presence in news on the web, the truth is that news plurality on the internet is exploding and the BBC's market share is comparatively small. Choice in news is expanding, not contracting.

If instead it's argued that, notwithstanding the breadth of choice, too many people choose to consume BBC News, then there are two other obstinate facts to confront. First, the BBC's charter calls for it to try to serve every household; if you want to abolish the BBC by all means advocate that, but if not, is it reasonable to criticise it for doing exactly what it has been asked to do? Second, the British public tell us that one of the key reasons why they use the BBC more than other news providers is because they trust it more than other news sources. If policymakers begin to regard high levels of public trust as a problem to be corrected, we really are in trouble.

Others – still apparently trying somehow to connect all this to the scandal at the News of the World – try to give the economic dominance argument more credibility by attaching it specifically to the question of news. In the Commons debate on phone hacking, David Cameron said that "there did come a point in recent years that the income of the BBC was so outstripping that of independent TV there was a danger of BBC News becoming rather dominant". In fact there has been no year in recent years when the BBC's income has "outstripped" that of its commercial counterparts. The BBC's revenues are in sustained relative decline and, under its new licence fee settlement, are likely also to decline in real terms, at least until 2017.

There is a broadcaster which is set within a few years to dwarf the combined income of every other UK broadcaster, and which is already by some margin the largest player in terms of revenue and market clout. It's a broadcaster which has been uncannily successful in persuading politicians and other opinion-formers to leave it out of the equation when people calculate and debate economic and editorial dominance. Funnily enough, it's also the broadcaster of which James Murdoch is chairman. Of course there's a place for a broader debate about the future media landscape, but it would be a pity if that deflected us from the most obvious and urgent matters arising from the News of the World case. Matters of personal conduct and criminality and above all of ethics and values.

If James Murdoch was giving his MacTaggart lecture this year instead of 2009 and in the (yes, admittedly unlikely) event that he turned to me for drafting advice, I'd suggest that he amended only one word in that ringing final sentence. The only reliable, durable and perpetual guarantor of independence is not profit. Nor who you know. Nor what corners you can cut. It's integrity.