This is a column about tawdry secrets. But first, I should declare an interest. I know the former deputy Labour leader Tom Watson a bit, even if our paths haven’t crossed for seven or eight years. At a crucial moment in this newspaper’s life he was fearless to the point of being foolhardy. I came to like and respect him.

The context today is a vociferous press campaign to prevent Watson from being elevated to the House of Lords. I have no strong feelings about that. But it’s as well for all involved to show their hand.

What are the tawdry secrets? The phrase was Tom Watson’s in a Commons debate in September 2010. The controversy over phone hacking in Rupert Murdoch’s empire was at its peak, and Watson was one of the few MPs willing to risk his neck to talk about it. His speech on 9 September was one of those rare parliamentary moments that were genuinely spine-tingling.

He told the Leveson inquiry that the Sun’s political editor had warned him: “Rupert Murdoch never forgets.”

A politician with an eye to advancement – or even survival – does not attack people who (pace Mark Twain) buy ink by the barrel. But that’s precisely what Watson did in that intervention, which questioned why virtually no MPs had ever stood up to the imperial might of the most powerful media magnate the world has ever seen.

“The truth is that, in the house, we are all, in our own ways, scared of the Rebekah Brookses of this world,” he began. Brooks was at the time clinging on to her job running Murdoch’s UK papers in the face of mounting evidence of rampant criminal behaviour under her own nose. Brooks was yet to stand trial at the Old Bailey, where her (successful) defence was that she had no idea what was going on in her own company. Watson knew – everyone knew – that Brooks – who to this day still has Murdoch’s absolute protection – was a bad enemy to make.

And yet he stood up in the Commons and told it like it was. “The barons of the media, with their red-topped assassins, are the biggest beasts in the modern jungle. They have no predators; they are untouchable. They laugh at the law; they sneer at parliament ... we are powerless in the face of them. We are afraid. That is the tawdry secret that dare not speak its name.”

He went further. About 18 months later the culture media and sport committee, of which he was an influential member, found Murdoch was not a “fit and proper person” to be running a major international company. That was a form of words which would help deal a fatal blow to Murdoch’s long-held ambition to attempt to dominate British broadcasting with BSkyB.

Watson knew this was dangerous stuff. He had already been trailed for five days by a Murdoch-employed private detective looking for dirt. In the preface to a book (Dial M for Murdoch, co-authored with Martin Hickman) he claimed his fight over phone hacking had led to the failure of his marriage, the loss of friends and many years of intense stress. He told the Leveson inquiry that the Sun’s political editor had warned him: “Rupert Murdoch never forgets.”

‘We should be grateful for his courage talking about one “tawdry secret” he exposed about parliament.’ Tom Watson at a parliamentary hearing into phone hacking in July 2011. Photograph: Reuters TV/Reuters

Murdoch’s pain over phone hacking continues to this day. It was recently reported that News Group newspapers shelled out £54m last year in legal fees and payoffs, leading to a loss of £68m at the Sun. Money is apparently no object in preventing any case getting into court that could show phone-hacking at the daily title as well as the now-defunct News of the World. Who knows what “tawdry secrets” might emerge if a case actually came to trial? Nor is the financial pain confined to the Murdoch titles. The BBC has reported that the total cost of settling phone-hacking allegations across the Sun, News of the World and Mirror titles could reach an eye-watering £1bn. Fleet Street will never forget the indignity of having to explain itself to Lord Justice Leveson.

Cut to this week’s papers and the fury of quite a few newspapers – including those owned by Murdoch, run once again by Brooks – at the prospect of seeing Lord Watson in the upper house. Watson has been – quite reasonably – criticised for the manner in which he used another speech in parliament, in 2012, to claim that there was “clear intelligence” of “a powerful paedophile network linked to parliament and No 10”. Those specific claims were plain wrong. The fact that the police and a number of experienced journalists were also taken in by the now-disgraced “informant”, Carl Beech, is no excuse.

Watson’s name features a number of times in this week’s report of the independent inquiry into child sexual abuse (IICSA) but he is not, so far as I can tell, directly criticised. The report is more concerned that, though there was ample evidence of sexual abusers linked to Westminster, there was a culture of deference towards politicians and other well-connected people. Others feature rather more centrally than Watson.

I have, as I say, no strong feelings about whether Watson deserves to be in the House of Lords. The quality of several recently ermined entrants is hardly testament to a beacon of democratic purity.

We should be grateful for his courage talking about one “tawdry secret” he exposed about parliament, just as the IICSA has sought to document the handling of other well-kept Westminster tawdry secrets.

There are interests to declare in these attacks on Watson. Newspapers perform a vital role in our democracy, but they do sometimes fall from grace. An MP who exposes the power of the press barons should not, a decade later, be damned without journalists at least acknowledging that they, and/or their ultimate bosses, are hardly disinterested parties. Enough of tawdry secrecy.

• Alan Rusbridger was editor in chief of the Guardian from 1995-2015