Former PR man David Cameron has delivered a masterclass in how not to handle a crisis

Paul Connew is a media commentator and broadcaster, former editor of the Sunday Mirror and Deputy Editor of the Daily Mirror, and co-author of After Leveson.

For a former professional PR man, David Cameron is fast becoming the PM whose ultimate legacy could turn out to be a monumental and self-inflicted PR disaster.

David Cameron, Yorkshire

If the prime minister's (mis)handling of the fallout from the Panama Papers revelations were a plotline from an episode of 'The Thick Of It', it would appear hilariously far-fetched. But, incredibly, this is reality..... and a brutal reality with the potential to force David Cameron out of Downing Street ahead of his own planned schedule and impact heavily on the outcome of Britain's EU referendum vote.

If Cameron had any doubt about the deep hole he's dug himself, he only has to review the newspaper front pages over the past 72 hours, re-watch the increasingly aggressive tone of the TV and radio coverage, or tap into the overwhelmingly hostile social media firestorm raging around him.

When bloggers and tweeters not normally supportive of Labour under Jeremy Corbyn's leadership start loudly echoing deputy leader Tom Watson's suggestion that David Cameron should resign, you know this isn't your run of the mill, here-today-gone-tomorrow type of political 'crisis' hype.

As a media commentator and PR adviser, I find it impossible to fathom David Cameron's strategic thinking (or lack of it) over the toxic issue of his father's company Blairmore and its offshore holdings. If the idea was to write the textbook on how NOT to handle crisis management, then the Prime Minister has certainly produced a masterpiece. And his personal background as a former TV PR executive makes it virtually impossible for David Cameron to shift the blame onto flawed advice from his Downing St communications advisers.

After five extraordinary days of shifting statements and half-truths, the prime minister finally came clean (as far as we know) in a 'fess-up' interview scoop with ITN's new politcal editor (and BBC fugee) Robert Peston on Thursday night. Triggering the Daily Mail's front page headline, 'PM: I DID profit from tax haven', with the sub-deck, 'He finally admits link to father's Panama fund'. With the Times leading on 'Cameron: I held shares in offshore tax haven', with the crucial sub-heading, 'PM reveals family profits at fifth time of asking'.

If the PM and any of his spin doctors were hoping that the Peston interview would defuse the crisis, they were hopelessly, helplessly wrong. If anything, it triggered a much tougher line from rival broadcasters, both miffed by the ITN 'scoop' and furious over the fact that they'd asked Cameron and his team exactly the same questions earlier in the week and been given far less candid answers. A point Sky News justifiably rammed home with repeated clips and references from their own political editor Faisal Islam's questioning of Cameron earlier, while over at the BBC Skills Minister Nick Bowles, rolled out to defend the prime minister, was treated to a ferocious, frequently interrupted grilling rarely seen on the Breakfast show. By the end of his round of the TV studios, Bone bore the haunted look of a man suffering from shellshock.

Churning out the line that Cameron hasn't broken the law and protesting that his initial evasiveness was a protective son's reaction to the media focus on his late father, simply didn't wash from the start, and have been swept down the plughole in the all-important court of public opinion. When you're the prime minister, full, frank disclosure DOES matter. Especially when you're spearheading the 'remain' argument in the momentous EU referendum decision facing the nation, especially when you're facing open revolt from the Brexit brigade in your own government and among much of the normally pro-Tory Press, and especially when your privileged upbringing is itself an issue in the age of austerity. And all this when you've made great PR play of cracking down on offshore tax havens and you're due shortly to chair an important international conference on the subject!

The tripwire on the ticking timebomb for the prime minister was set from the moment number 10 issued that stonewalling 'it's a private matter' response after the Panama Papers revealed his father's secretive offshore Blairmore company, handling tens of millions of pounds for wealthy individuals anxious to avoid tax. When that didn't quell the media and rival politicians' questions, there was the ludicrous statement: "There are no offshore funds/trusts which the PM, Mrs Cameron or their children will benefit from in future."

Eh? Even my 15-year-old, preparing for his economics exam, immediately asked 'But what about the past, dad?'. Quite. And if the prime minister and/or his Downing Street media team didn't anticipate Fleet Street and broadcasting's finest firing that question back, then they really do make 'The Thick of It' look more like a documentary than political satire.

Still the questions fly thick and fast. If Cameron didn't feel there was something questionable about his holdings in Blairmore, why else would he sell his shares in January 2010 and fail to mention it during that year's general election campaign? Why didn't he declare his stake in Blairmore in the 2009/10 parliamentary Register of Members' Financial Interests? Did he benefit, or does he stand to benefit in his mother's will, from another part of his father Ian's estate based in another tax haven, Jersey? The public are also entitled to ask for a better explanation from the prime minister why he lobbied the EU not to mount a crackdown on offshore trusts in 2013 – a stance that sits more than a little oddly with his more recent claims to be the champion of combating global tax avoidance

I'm told the prime minister is a keen reader of Times political sketch writer Patrick Kidd's column. Well, the opening paragraph of Kidd's Friday column, the morning after his confessional encounter with Peston, won't have heped Cameron digest his breakfast. Under the headline, "Blairmore? It simply gave savings a suntan?", Kidd wrote: "The polish has gone from the prime minister. David Cameron, whose cheeks usually resemble sides of ham that have been buffed for a month by a madrileno butcher, looked tired and dappled as he attempted to draw a line under the concerns about his father's finances."

Growing Labour calls for the prime minister's resignation remain unlikely to bear fruit (but shouldn't be discounted if further skeletons emerge). But undoubtedly public trust in Cameron has been heavily, if not quite fatally, wounded. And that matters massively in the context of the momentous EU referendum vote to come on 23 June. Although none of the Tory Brexiteers, including Boris Johnson and Michael Gove, are saying it publicly, there is certainly private delight at the prime minister's public humiliation and the damage it does to him as remain's commander-in-chief.

The crisis surrounding Cameron also poses something of a catch-22 dilemma for the Labour leadership. On one hand, they scent blood with influential backbencher John Mann demanding the prime minister's resignation, and deputy leader Watson suggesting Cameron could be forced into resignation. On the other, the Labour party is (despite Jeremy Corbyn's past Euroscepticism) strongly committed to supporting the Yes campaign. And some on Labour's front bench fear that if Cameron were to fall now, Brexit poster boy Johnson would be the obvious successor in what might prove a huge and possibly decisive coup for the out campaign.

If the old PR man in David Cameron is counting on finally fulfilling his long promised, long-delayed pledge to publicly release his tax returns as the key weapon in a reputation-rescuing, damage limitation strategy, then he may well be whistling in the wind.

And that's bad news for those of us who don't want the legitimate fallout and furore from shady dealings in sunny tax havens to overshadow the momentous question of the UK's future, inside or outside the EU.

Paul Connew is a media commentator, PR consultant, broadcaster and former editor of the Sunday Mirror and deputy editor of the Daily Mirror