Rupert Cornwell: Spot the hoax in the land of Fox News

Out of America: 'Balloon Boy' took the nation in – but it's even harder to distinguish fact from fiction among the polarised cable TV networks

This summer, I finally managed to see Schtonk!, the German movie about the fake Hitler diaries affair of 1983. As hoaxes go, this was among the very best: a rip-roaring, reputation-shredding, utterly riotous scam that provided innocent entertainment for all (except for the hapless Stern magazine, which wasted millions on buying and publishing its "scoop" of the century). The movie, itself now almost two decades old, is no less terrific. It also has a very modern relevance. These days, America lives in a permanent state of schtonk.

Hoaxes, intended or accidental, seem to be everywhere. The anniversary of 9/11 was marked here in Washington by breathless cable TV reports of shots being fired in a terrorist attack near the Pentagon – based, it soon transpired, on intercepts of coastguard radio chatter about a routine training exercise, in which not a single shot was fired.

That one was an honest, if credulous, mistake. Not so the "Balloon Boy" affair, when television channels dropped everything to track the progress of a silver-blue balloon floating around the Colorado heavens with a six-year-old aboard. The pictures were fabulous, as riveting as the human drama that seemed to be unfolding. The only problem was that the child in question was safe at home in the attic; the authorities now know the whole thing was a stunt organised by dad to get the family on to a reality TV show (which it undoubtedly one day will).

Last week, yet another hoax made the headlines, in the shape of a press conference supposedly called by the US Chamber of Commerce to announce that the powerful business group was dropping its long-held opposition to climate change legislation. That really would have been a news bombshell. Except that it wasn't true. The whole thing, complete with a fake press release and an imitation chamber logo on the lectern at the venerable National Press Club in Washington, where the event was to be held, was got up by environmental activists. Proceedings ended with a hilarious confrontation between representatives of the real and bogus Chamber of Commerce, each claiming the other was an imposter and demanding to see his business card. But not before a news agency and a cable network had put out stories they were forced to kill a few minutes later.

Then there are what one might call slow-motion hoaxes that refuse to lose currency, however comprehensively disproved. Some people still really do believe that the healthcare legislation under debate by Congress calls for "death panels" of officials who would decide which patients would receive treatment and which would be left to die. Nor have "birthers" entirely disappeared – people who insist, irrefutable documents to the contrary, that Barack Obama is not a US citizen by birth and is thus disqualified from being president.

But these are only extreme examples. Today's round-the-clock bombardment of information, delivered faster, in greater quantity, and from more sources than ever before, so easily blurs the line between reality and illusion. You are told everything and the opposite of everything, sometimes in the same sentence. Truth ought to be growing more objective; in fact, it's becoming more subjective. With a palette of alternative realities on offer, you can believe what you want to believe, and find evidence to justify that belief.

The nature of hoaxing has also changed. The Hitler diaries, and Clifford Irving's fake autobiography of Howard Hughes – the Schtonk! romp's closest challenger for best hoax of the modern era – were both motivated primarily by money. They were frauds made possible by greed, and by huge potential returns that overwhelmed common sense.

Human nature, of course, hasn't changed, but technology has. These days the combination of ferocious media competition and the sheer speed of communication is the great enabler of hoaxes. And cable news, with its twin needs of material to fill the screen 24/7 and of ever more strident opinion to win the ratings war, is the most vulnerable link in the chain. Newspapers may be cutting back across the board but (in their print manifestation at least) they usually have a few hours to winnow fact from fiction. Not so the video wire service that is TV news.

And that's where the problem gets serious. Of course the main cable networks aren't hoaxers. Increasingly, however, they package reality to cater for different political tastes. If you're a conservative, you gravitate to Fox, with its battery of Obama-deriding hosts. Liberals prefer MSNBC, while CNN, the grandfather of cable news, sits awkwardly somewhere in the middle. In short, you can pick your poison. And that's why this Democratic administration is getting rattled as Fox pulls steadily further ahead in the ratings.

Every administration wants to control the media, but the Obama team is taking its battle with the Murdoch-owned Fox to extraordinary lengths. A few weeks ago, senior emissaries from the two sides met at a Manhattan restaurant to mend fences. Fox insists that its news coverage and its commentators are separate; the latter might have a point of view, but not the former. The administration, however, isn't buying, arguing that Fox's slant was reflected not only in how it covered events, but what it chose to cover. Today, Obama and his top officials refuse to appear on a network they regard as little more than a mouthpiece for the Republican party. "We simply decided to stop abiding by the fiction that Fox is a traditional news organisation," a presidential spokesman says. Ouch.

But in this fight, the winner won't be the White House. Even Fox's rivals are uncomfortable at what's happening; the last thing they want is to be portrayed as patsies of the administration. The "fair and balanced" network, meanwhile, revels in the role of bad boy, the speaker of truth the government wants to silence. So we punters must decide, silently voicing the words of the comedian Lily Tomlin: "I try to be cynical, but it's hard to keep up." Oh, for the simpler age of Schtonk!.