It's a melancholy fate for any writer to become an eponym for all that he despised, but that is what happened to George Orwell, whose memory is routinely abused in unthinking uses of the adjective "Orwellian". On Monday it is "Orwell Day", the 63rd anniversary of his death. This year also marks the more pleasantly round number of 110 years since his birth (on 25 June), so there is a Radio 4 series about him forthcoming, and Penguin are reissuing his works, including a standalone edition of "Politics and the English Language".

"Politics" is Orwell's most famous shorter work, and probably the most wildly overrated of any of his writings. Much of it is the kind of nonsense screed against linguistic pet hates that anyone today might compose in a green-text email to the newspapers. So why do so many people still genuflect in its direction? Media invocations of Orwell's virtues increased markedly after 9/11, when it seemed to some opportunist intellectuals as though his life and oeuvre prophetically justified the pre-emptive invasion of far-off sandy places. But the enduring popularity of "Politics and the English Language" in particular derives from two things. First, it gives a list of writing tips. (Aspiring writers love to collect lists of writing tips instead of actually writing.) Second, it is savagely contemptuous of politicians and what they say, an attitude that never goes out of fashion. But both these aspects of the essay are problematic.

"In our time, political speech and writing are largely the defence of the indefensible," Orwell writes, in the most celebrated passage. "Things like the continuance of British rule in India, the Russian purges and deportations, the dropping of the atom bombs on Japan, can indeed be defended, but only by arguments which are too brutal for most people to face, and which do not square with the professed aims of political parties. Thus political language has to consist largely of euphemism, question-begging and sheer cloudy vagueness." In the essay's peroration, he concludes: "Political language […] is designed to make lies sound truthful and murder respectable, and to give an appearance of solidity to pure wind."

This is put with exhilarating ferocity, though Orwell was not, as some assume, the first to notice the phenomenon. (Confucius had complained millennia before that politically motivated misnaming led to the corruption of society.) Orwell nods here by using the phrase "the Russian purges" descriptively himself: euphemising the show trials and mass executions as "purges" was a way of metaphorically justifying them as a purification of the body politic. But he offers other bloodily fine examples from his era: "pacification" of villages by bombing, or "rectification of frontiers" by forcibly ejecting people from their farms.

What is worrying, however, is that Orwell's diagnosis of "cloudy vagueness" and "pure wind" might seem to sanction an impatient dismissal. Should we just assume that everything politicians say is hot air? To do so would be to let our guards down. Political rhetoric now as in Orwell's day exploits not only euphemism ("austerity") but dysphemism ("skivers") and loaded metaphor ("fiscal cliff"): in our time, weaponised soundbites are deliberately engineered to smuggle the greatest amount of persuasion into the smallest space, to be virally replicated on rolling news. In my book on modern political rhetoric, I called this Unspeak. Rather than waving it away as "pure wind", it is necessary to listen all the more closely to this stuff, because you need to bring the buried argument out into the open in order to defeat it.

Take the ubiquitous calls today for European countries to do just what will "reassure the markets", as though holders of government bonds were trembling, paranoid little flowers who must be psychically coddled at all costs. It implies quite unashamedly that it is after all fund managers and central bankers, not prime ministers or presidents, who are sovereign. Paying attention to this idea of "nervous" markets who "need" to have their "confidence" bolstered tells us something important about the relative respect accorded by our masters to "the market" on the one hand and democracy on the other. (Of course, "democracy" itself has long been a contested term, as Orwell recognised.)

Orwell's assault on political euphemism, then, is righteous but limited. His more general attacks in "Politics" on what he perceives to be bad style are often outright ridiculous, parading a comically arbitrary collection of intolerances. Orwell was right that "the slovenliness of our language makes it easier for us to have foolish thoughts". But what he called "the fight against bad English" is too often understood, thanks to the perversities of his own example, as a philistine and joyless campaign in favour of that shibboleth of dull pedants "plain English".

His essay comforts, for example, the kind of Little Englander of the verbals who is suspicious of words from beyond these shores. If you ever feel tempted to say "status quo" or "cul de sac", for instance, Orwell will sneer at you for "pretentious diction". Why pretentious? Because these phrases are of "foreign" origin. "Except for the useful abbreviations i.e., e.g., and etc …" Orwell declares, "there is no real need for any of the hundreds of foreign phrases now current in the English language." Yet if we strip the language down to what there is a "real need" for, whither poetry? Allow only the words that Orwell thinks necessary, and the resulting stunted lexicon is itself a kind of functionalist, impoverished Newspeak.

Nor, according to Orwell's linguistic xenophobia, is there any excuse for forming new words from Latin or Greek, such as, er, xenophobia. He cites the shockingly ugly examples of "predict" and "extraneous". Orwell never explains why the stolid old Anglo-Saxon should be any more "clear" than such newfangled horrors; as "predict" and "extraneous" demonstrate now, words minted from the classical will very rapidly seem entirely normal.

Orwell's eccentric final tip-list includes "Never use a long word where a short one will do" (why ever not?), and "Never use the passive where you can use the active." No good reason is offered or indeed imaginable for always avoiding the passive, though Orwell did thus influence a whole generation of incompetent style-guide composers who repeated this loony stricture as gospel.

In any case, the tips are all undone by the last: "Break any of these rules sooner than say anything outright barbarous." But, the eager student might ask, how is one to tell whether what one has said is barbarous or not? Orwell is silent on the matter. Presumably it ends up being a question of taste. Orwell's own taste was notably dubious when applied to the work of others: his essay about the first three of TS Eliot's Four Quartets, for example, is cloth-eared and bigoted. (Because he hates Eliot's religion, he is sure that the poetry must be bad.) Orwell even concedes, at the end of "Politics", that you could follow all his rules and "still write bad English". But then, compiling lists of writing tips is a pleasant work-avoidance strategy for writers, too.

• Steven Poole's most recent book is You Aren't What You Eat (Union Books).