Kingsley Amis used to have no qualms about attacking the "terrible compulsive vividness" of his son's writing. He even went as far as to say he could never finish reading his novels. "It goes back to one of Martin's heroes - Nabokov. I lay it all at his door - that constant demonstrating of his command of Englishness." These accusations of unnecessary verboseness have haunted Amis' illuminated career.

I actually think these criticisms are unfair when it comes to his novels - they may not always be easy to read, but there is nothing wrong with having an unmistakeable style or with sending the reader to the dictionary every few paragraphs. But the story is different when it comes to his political writing.

Last week on Cif, Michael White discussed Amis' latest polemic, recently published in the Times. White's article focused on Amis' critique of "liberal relativism". But perhaps even more significant than this is what the piece tells us about the potential pitfalls which can emerge when a novelist dabbles in explicitly political writing.

There is nothing original in Amis' argument: September 11th, we are told, "is the most momentous event in world history since the end of the cold war." The "war on terror" may not have been fought effectively, particularly in Iraq, but there can be no shying away from the fight. "Liberal relativists" who try to explain away the death cult that lies at the heart of Islamism are fools, "the Islamists are fanatics and nihilists who, in their mad quest for world domination, have created a cult of death." In short, this is the recycling of the arguments which led to Mart being heralded as the high priest of a new "Blitcon" movement at the heart of British literature.

I'm less interested in the accuracy of these claims (discussed in the White piece and the debate which follows), than in what they tell us about the relationship between novelists and political writing. George Orwell always advised never to use a long word when a shorter one would suffice. On top of that, he was both a political writer and a novelist. Perhaps it was this seeming disdain for the importance of aesthetics, which has led some to question the quality of his novels. Either way, Amis would do well to consider his words. Political writing should aim to clearly explain the situation at hand. Unlike the novelist, who consciously uses a fictional world as their starting point for explaining reality, the role of the political writer is to describe and analyse the world as it is.

In an interview, Amis said the following about Orwell: "My elder boy used to be completely dismissive of any view that didn't proclaim that George Orwell was the greatest writer of the 20th century. He was going through his commonsensical, middle-teen years. But now he reads the Iliad and he looks back and says, 'compared to Orwell this is just magnificent.' But I am steering them to my particular line, you know, Nabokov, Bellow, Joyce. And we'll see what happens." And Amis is right: aesthetic grandeur is vital to a novel's greatness. But political writing depends on a different type of power, embodied in the clarity for which Orwell was justly famed. When he writes about politics, Amis doesn't seem to get this.

Here are three examples of how Amis' prose does nothing to elucidate the matter at hand:

• "The solecism, that is to say, is not grammatical but moral-aesthetic - an offence against decorum; and decorum means 'seemliness', which comes from soemr, 'fitting', and soema, 'to honour'."

• "Our own performance, in what we may limply but accurately call the struggle against those who use terror, has also shown signs of mass somnambulism and self-hypnosis. This is true at the executive level, insofar as the Iraq misadventure (and much else) is a corollary of the neoconservative 'dogma'; and it is true on the level of individual response."

• "Much of our analysis [of 9/11], perhaps, has been wholly inapposite, because we keep trying to construe Islamism in terms of the ratiocinative. How does it look when we construe it in terms of the emotions? Familiar emotional states (hurt, hatred, fury, shame, dishonour, and, above all, humiliation), but at unfamiliar intensities - intensities that secular democracy, and the rules of law and civil society, will always tend to neutralise."

As I said before, this isn't a gripe about having to run to the dictionary (ratiocination is the process of logical reasoning), but at the sheer inappropriateness of the prose. With such convoluted wording, I expect some stunning insight.

I don't expect to have to scratch around for a few minutes before discovering that there's nothing interesting being said: British intellectuals are offensive for referring to 9/11 as November 9; the "War on Terror" (I prefer inverted commas to "limply but accurately") has been poorly fought; too much effort is spent rationally looking at the political motives for Islamism rather than the religious passions which inspire it. Is any of this stuff really new to anybody? The "Amis-ness" of the prose should not blind us to the fact that we aren't being offered any new insight.

It's been said before that too many novelists have tried to offer us the definitive literary statement on 9/11. In a devastating review of Ian McEwan's Saturday, for example, John Banville quipped: "If we all have a novel in us, nowadays it is likely to be a September 11 novel." This rush to surmise the Zeitgeist has often been an unfortunate one, with few benefits for either literature or our understanding of the "war on terror". But if there's one thing worse than a rushed and superficial novel responding to 9/11, it's an over-ponderous polemic by a verbose novelist.

I'm not suggesting that novelists shouldn't also write op-eds. As has already been noted, whatever his other shortcomings, Mr Orwell did a reasonably good job at both, and there are others who have done the same. But, while novelists may be the best-placed public intellectuals to help us understand the world around us, that does not mean they should be granted carte blanche to spew forth whenever they like.

Novelists explain the world through the novel, and we should watch very carefully when they switch medium, because they often do a decidedly shoddy job. Amis has previous on this, and not just when it comes to the "war on terror". In a feature for the Guardian, for example, he shadowed Tony Blair during his last days as prime minister. Aside from the occasional flash of insight, there was simply nothing there.

In Experience, Amis responds to his father's criticisms of Nabokov, and by extension himself. "Style is morality: morality detailed, configured, intensified." This seems to be a step too far. Declaring style to be a value is one thing, calling it the embodiment of morality another. If style serves to obfuscate the message, to hide the author's lack of real insight, it is anything but morality.

Style should serve to strengthen the author's message, whether they are writing a novel, a poem or a column on Cif. While I wouldn't want to be so trite as to tell Amis to stick to the novels, I would suggest he thinks very carefully before he wades in so explicitly into the debate over the "war on terror", lest his interventions serve to weaken his justly deserved reputation.