I've just read one of the worst speeches by a British prime minister it's been my misfortune to encounter in 40 years following politics. Wilson had folksy evasiveness; Heath, wooden principle; Thatcher, tin-eared persistence; Blair, slimy charm. In every case you could tell why they'd got the job, even when you hated what they were doing with it.

But this? This hole in the air encased in a suit of clunking verbal armour? This truck-load of clichéd grandiloquence in hopeless pursuit of anything that might count as the faintest apology for an idea? Words fail me.

They certainly failed Gordon Brown, addressing the European Parliament this week. No wonder everybody's now watching the MEP Daniel Hannan's riposte, uploaded on to YouTube - for the sheer, blessed relief of finding anyone still standing as the grey ash came bucketing down.

Where shall I begin? Shall I bother? Is he worth it?

“It is thanks to the work of all of you and the generations whose work we continue that we enjoy a Europe of peace and unity which will truly rank among the finest of human achievements” would be fine - no, not fine; pardonable - if no more than a paragraph of pompous pleasantry, to puff the hard argument. But hard argument came there none. It was all puff.

“So I stand here today proud to be British and proud to be European: representing a country that does not see itself as an island beside Europe but as a country at the centre of Europe, not in Europe's slipstream but firmly in its mainstream.” Not an island? Airborne in a slipstream? In a river in a mainstream? So much for geography, aeronautics and hydraulics. Now for history.

“Friends, today there is no old Europe, no new Europe, no East or West Europe. There is only one Europe, our home Europe”... and on we go. A list of truths, half-truths and untruths follows: claims about EU progress, some of which Mr Brown has actively blocked.

The market crisis is then dispatched by means of a clutch of attempts at wordplay (“markets should be free but not value-free”... “freedom need not be a free-for-all” ...“being fair is more important than being laissez-faire”) so maladroit as to deserve inclusion in any young speechwriter's textbook warning against laboured verbal conceit. Mr Brown then repeats himself at greater length but with no greater felicity.

And so on. There are, it is true, a couple of harder-edged paragraphs. Here Mr Brown lambasts as immoral the banking system that for a decade he praised and harvested. There is no hint even of ruefulness, and we move to a PowerPoint-style presentation of some perfectly routine aims for the G20 summit in London next week.

It is not worth detaining you with the peroration, which lasts for pages (“So let it be said of us that at the worst of times, in the deepest of downturns, we kept to our faith in the future and together we reshaped and renewed the world order for our times”). Nor need we bother with “a quote I love from one of our most famous Europeans, Michelangelo”, whose selection represents an achievement by Mr Brown: he has managed to find something banal in Michelangelo's output.

But then, as one of our great Europeans, Dr Johnson, didn't quite say: the prospect of the G20 summit is concentrating Mr Brown's mind wonderfully. So much so that, as I write, he's airborne again, after touching down in Brazil in the hope that a little of Pelé's (or President Lula's) South American stardust will rub off on him, and bound for a Chilean seaside resort where a ludicrous “progressive governance” summit has failed to attract any other national leader beyond Chile's, Argentina's and Norway's.

Even the Spanish are sending only a ministerial understrapper. But Peter Mandelson will be there, after touching down briefly in Brazil to contradict Mr Brown's new approach to capitalism.

What a preparation for the London ExCeL Centre, which is squeezing in Mr Brown and his global pals between the London International Dive Show and MillionaireMind Intensive UK Live. My Times colleague Sam Coates blogs that the G20 gig is costing more than £4 million an hour. In the wake of the disappointment that will follow we can already anticipate Mr Brown's next speech: “Friends, just as we had the G20, so it is now right that we move forward together as a nation to the G77...”

Enough. There's something wrong in our politics, something big and bang-in-the-middle: a howling question that is not about the global economy at all. It's about domestic leadership. It's about Mr Brown. He isn't any good. He's failing. He's embarrassing. He's dreadful. His colleagues know this. Yet they are gripped with a terrible fatalism, sliding towards election defeat as though catastrophe were unavoidable.

Defeat isn't, but catastrophe is. New Labour has modest achievement to its credit; and as to its two great blunders - Iraq and the credit bubble - the Tories have been in there too: up to their necks. It is still possible to pull things back quite some distance. But not with Mr Brown.

Don't rule out an October revolution. Don't rule out Mr Brown himself staring a 2010 defeat in the face, and deciding to run away. He's avoided two elections already - for the leadership, and then for an early general. He can duck a third. But he needs a new speechwriter.

Well here goes: “...I took the helm just as we faced a time of unprecedented anxiety and economic trouble. I said I'd steer and I did. I took the hard decisions. I know they were right. The worst is over, and I'm confident Britain will understand this in the years ahead.

“But in politics if you do wade in, if you do get to grips with difficult and unpopular measures, if you do tell unwelcome truths, you must become associated in the national mind with times of crisis and trouble. The page my name heads is a dark page. I would love to be the man who turns it. But it would be better if the baton now passes, and a fresh figure takes us onward. This is the sacrifice I must make.”

Then, indeed, might we paraphrase that great European, William Shakespeare, writing about that great European, Macbeth: “Nothing in his political life became him like the leaving it.”

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