So much falls into place with the revelation that Tony Blair became godfather to one of Rupert Murdoch's two young daughters and attended their baptism on the banks of the river Jordan last year. True, it isn't yet clear whether Blair had agreed to become a godparent while he was prime minister [see footnote], and the ceremony did take place after he had left office, but the important point is that the relationship underlines Murdoch's deep entrenchment in British political life.

Murdoch's third wife, Wendi Deng, who let slip the information in an interview with Vogue, described Blair as one of Rupert's closest friends. Blair's account of the relationship in his memoirs is somewhat different, portraying Murdoch as the big bad beast, who won his grudging respect. That is clearly disingenuous. As other memoirs and diaries from the Blair period are published, we see how close Murdoch was to the prime minister and the centre of power when really important decisions, such as the Iraq invasion, were being made.

Blair and Murdoch didn't have to be bosom buddies for the relationship to be counter to the interests of a healthy national life and politics. As Lance Price, the former Blair spin doctor, has said, Murdoch was one of four people in Britain whose reaction was considered when any important decision was made during the Blair years.

It is simply unacceptable for a modern democracy to allow a foreign media tycoon, whose interests are exclusively limited to his business, to act as the national puppeteer, and one hopes that the phone-hacking scandal will eventually result in a stake being driven through the heart of this particular corruption. But there is still, I suggest, some way to go.

Murdoch is the single most corrosive individual influence in this country since the war. The rejoinder to this is that he saved the press from the print unions and ensured media plurality. Even if this is true, the benefits came with a price tag we could not afford. None of our political leaders felt able to stand up to him. John Major briefly considered it, and Tony Blair was lobbied by Chris Mullins MP, the account of which is published in his diaries, A Walk-on Part, but in three decades no one found the resolve to restrict Murdoch's access to No 10 and stop his menacing of the political classes.

Real political power always works unseen, and that is how Murdoch has pulled the levers in British society. Prime ministers who accept Murdoch's support end up doing his bidding. A lot more has yet to come out about the proximity of the prime minister to News International in the run up to the BSkyB deal. Several of Blair's key ministers (John Prescott, Gordon Brown, Jack Straw and Tessa Jowell) were hacked during his administration, yet Blair has never seen fit to criticise Murdoch on this astonishing breach of national security. But then how could he when he was little Grace's godfather, and sees the Murdochs socially in New York?

We should welcome Wendi Deng's indiscretion – which it surely was since Blair has obviously tried to keep the matter confidential – because it establishes beyond doubt the nature of the bond between Blair and Murdoch, which is far closer than the reluctant affinity that Blair has described.

At the beginning of the political season, this story must surely renew our interest in David Cameron's entanglement with Rebekah Brooks during the months when the merger between News International and BSkyB was being considered by the government. When it comes to Rupert Murdoch and his people, nothing – even a religious ceremony on the banks of a holy river – can be taken at face value. As for the devout Tony Blair, he should ask himself who was really established as the godfather during that ceremony.

• This article was amended on 9 September 2011. A spokesman for Blair's office has asked us to clarify that he was not asked to become a godfather while he was prime minister and did so three years after he left office. The original included the phrase "I feel sure, and it seems highly likely that Blair did indeed ask Gordon Brown to intercede with Tom Watson MP, Brown's ally, on the phone-hacking scandal". This has been deleted because Blair has consistently denied that this was the case. Blair has also asked us to make clear that he has criticised phone hacking as "beyond disgusting and sickening actually".