Is it possible to be too plain speaking? Harriet Harman sometimes makes you wonder. Uncomplicated by humour, intricacy and, for much of the time, any evidence of considered thought, her oratory exhibits an unwavering commitment to simple expression. One thinks, for example, of this recent comment on Fred the Shred's pension: "It is not acceptable and therefore it will not be accepted."

Her feats of clarity have impressed even the Plain English campaigners. Three years ago, when Harman was minister for constitutional affairs, hers was the first department to publish legislation, the draft Coroner Reform Bill, with a translation into what she called "ordinary English" alongside the usual legalese. "The aim is to link government more effectively to parliament and the public," she explained. "All that most members of the public can do is listen to the debate professional politicians are having about the bill … so it's hard for people just to see for themselves what a bill would mean to them."

Which, when translated, turned out to mean: Ms Harman is preternaturally sympathetic to the interests of the Primark-going classes and therefore better suited than any of her rivals to be deputy leader of the party.

Perhaps it is thanks to Harman's influence that the prime minister is also increasingly translated into plain English. Compare "I wake up in the morning thinking what we can do to help" with his allusion, in a speech delivered 1994, to "post-neoclassical endogenous growth theory". Abandoning the Ed Balls demotic, the prime minister now appears to take inspiration from an easy-to-follow book by Dr Seuss: Mr Brown can moo, can you?

For example, in case the public should find it hard to process the meaning of "I wake up in the morning thinking what we can do to help", Mr Brown is careful to repeat the line almost every time he addresses the public. This way, even hardworking toddlers can understand that they are being patronised.

It seems that one thing that occurred to Mr Brown recently, when he woke up in the morning, was a helpful fiscal procedure called "quantitative easing". He went and told Harriet Harman about it. A week or so ago, Harriet duly told the House of Commons that "in respect of quantitative easing, the monetary policy committee has introduced up to £75bn extra that will be put in the economy".

Given Harriet's commitment to simple speech, as well as the airy way in which she made this incomprehensible announcement, it's possible she thinks quantitative easing is so commonplace an expression that any explanation would be an insult to the intelligence of ordinary people. Unlike the legal language in her coroners bill, whose translation, unfortunately, almost no ordinary people ever appreciated because the bill was all about tinkering with the legal system and therefore of interest only to lawyers.

Quantitative easing, on the other hand, is of tremendous interest to anyone who thinks that the £150bn further agreed by Alistair Darling is a lot of public money and wonders where in the economy it is going to be, to use the technical term, "put". Maybe, since there are no clues from the government, we are meant to work it out for ourselves. We've most of us heard the word quantitative, or at least, quantity, haven't we? Plus, Boots is full of remedies for easing this or that. So put them together and what have you got? The product increasingly known as QE: a measurable amount of making something better. Perhaps it contains tea tree oil. At any rate, this balm sounds just the ticket if you ever have the misfortune to get mixed up in an extraordinary rendition. Sorted.

Or it would be if some trusted financial interpreters from outside the government were not suggesting that QE is, in fact, a glib acronym for a Japanese euphemism for a potentially disastrous variation on printing money which has only ever been tried, with debatable success, in Japan. But definitions vary. Within Westminster, there was some confusion at a committee of experts about the exact relation between QE and the "Asset Purchase Facility" recently discussed in letters between Mervyn King and Alistair Darling. Aren't they the same thing, ie, printing money? Certainly not, sniffed one witness, the new deputy governor of the Bank of England, a Mr Tucker. Any new money involved would not be printed, he insisted, but "created". But could it, once created by a divine agency, be later turned into notes by some sort of sub-lunary outfit? Like a bank? An awestruck committee did not inquire.

Even if the public is accustomed, by now, to looking up all the different kinds of City junk on Wikipedia, it is surely the government's responsibility to explain this latest bit of jargon, given that it appears to be Treasury policy, as opposed to a Ponzi scheme, or a CDO or some other demi-corrupt speculator device. Maybe it believes the concept is beyond us. Is it any more complicated than the Oxford professor for the public understanding of science, Marcus du Sautoy, explaining the surprisingly high probability of two people sharing a birthday? Or how about giving the job to the panel from Melvyn Bragg's In Our Time which recently did such a brilliant job with Schrödinger's cat?

On the other hand, the cat theory does feature a cat. In all the jargon and circumlocution to emerge in this recession, the words quantitative easing stand out for having no ostensible relationship with the process they are meant to describe. QE looks less like a squalid official euphemism, along the easily decipherable lines of "collateral damage", than a piece of deliberate concealment.

But you have to admire the skill that has gone in condensing such a wealth of artful dishonesty into two words or letters. Until now, the government's preferred technique, when troublesome information could not be straightforwardly suppressed, was to inter it within thick layers of protective prose. From the monster Hutton report, to the unspeakably written EU constitution turned Lisbon treaty, and Lord Stern's scary, strictly unreadable climate change epic, crushing tedium and dreary appendices have proved superbly effective diluters of democratic debate, even on the most urgent topics. At least the information was in there, somewhere. How, Harriet Harman would once have asked, can members of the public discover what QE means to them from a random pair of words, presented without so much as a footnote?

It is quite a theme with Brown, these days, to deprecate bankers who "did not understand the risk in which they were involved" and to scorn anyone who contradicts his own analysis as a boneheaded liability. "If you do not understand," he told the BBC's Julian Worricker on a supposedly empathetic phone-in last week, "and others don't understand what the problem is we're dealing with, we'll never solve it."

Unless, as now, he manages to pass off his favoured solution, that of PM, as QE: a cross between a popular TV programme, our beloved queen and a generous dose of laxative. Every morning, when he wakes up, Gordon must think about this and have a right laugh.