Dominic Lawson: If you want to detect hypocrisy in a public figure, try Utley's Law

I'd be fascinated to know if Labour MPs were less generous than their Tory rivals

Is Greenness the path to Godliness? To judge by recent lectures from the grandest pulpits of the Church of England, that is the official view of our national church. Not so very long ago it published a set of new "Green commandments" entitled "How many Lightbulbs does it take to change a Christian?" and the Prince of Wales's favourite clergyman, the Right Rev Richard Chartres, declared that flying was "a symptom of sin".

Last week, however, the academic journal Psychological Science issued what amounted to a peer-reviewed rebuttal of this peculiarly fashionable form of moral teaching with a paper entitled '"Do Green Products Make Us Better People?'. Based on a controlled experiment tracking 156 students from the University of Toronto, the authors, Drs Nina Mazar and Chen-Bo Zhong, concluded that the answer was: no, and possibly quite the contrary. Their study, which admittedly seemed somewhat contrived even by the standards of psychological experimentation, found that "purchasing Green products may produce the counterintuitive effect of licensing asocial and unethical behaviours by establishing moral credentials..."

Actually, this is something which the Church of England's Bishops ought to understand very well: it is reminiscent of the charge against the Pharisees in the New Testament – that they confused ritualistic acts with genuine morality. An analogous accusation has rightly been made about the now vast business of carbon-offsetting: that it is the modern equivalent of the mediaeval Roman Catholic practice of the purchase of indulgences.

Perhaps, therefore, it should not have come as such a surprise that two out of the three Labour MPs recently charged under the Theft Act were also the two elected politicians most admired within the Green movement: Elliot Morley and David Chaytor. This newspaper published a heartfelt elegy for Mr Morley after his collar was felt by the cops: "Most of all he became concerned about climate change... This man spent all his long ministerial career defending the environment... Say what you like. Cast what stones you want. This is the truth." David Chaytor, meanwhile, is the long-serving Secretary of Globe UK, the British branch of the international network of environmentalist parliamentarians. Naturally both men protest their complete innocence of all the charges of theft, so it is too early to say whether they are a slam-dunk case for the Canadian psychologists' theory that establishing one's virtuousness as a Green makes one more likely to transgress in other matters, on the grounds that one has satisfactorily demonstrated one's essential goodness.

This might seem like marvellously fresh ground for a novelist – were it not for the fact that some of the great writers of the past had already covered something of the same territory. The most comical observation in the English novel of a related phenomenon is Charles Dickens's character of Mrs Jellyby in Bleak House. She devoted all of her attentions to a project in Africa called the Borrioboola-Gha venture – while remaining completely, even cruelly, blind to the needs of her own children, who therefore lived in conditions of squalor and neglect. Hence the tragic-comic exclamation of one of her little daughters, shivering in the cold of an unheated London home: "I wish Africa was dead!". Dickens gave this chapter of Bleak House the unforgettable title "Telescopic Philanthropy".

Mrs Jellyby, though monstrous in her own way, at least was spending her own money on the Borrioboola-Gha project, rather than everybody else's. The modern-day environmentalist politician wants to force the entire nation to pay more for its fuel, and, if necessary, to shiver in the cold, in order to "save the planet". This is not charity, but compulsion, and therefore nothing to do with individual moral decisions.

This does not much bother the Left, which, ever since Rousseau, has regarded the state, rather than the individual, as the source of a people's moral salvation. It is a bizarre, but surprisingly tenacious, view. As those Canadian psychologists suggest, the consequence might be that those politicians who regularly vote for "virtuous" higher taxes (to fund their various schemes of redistribution from the well-off to the less so) are actually more likely to exploit their hold on the public purse to their own personal benefit.

This does indeed seem to have been borne out by the great Commons expenses scandal. Despite the long-standing view that Tories are the most venal of politicians, it turned out that Labour MPs took the greatest amount of the public's money through so-called "home-flipping", in which they gamed the expenses system to set up personal property windfalls. Of course, many Tories were at it too, but the whole episode ought to have destroyed the view that the Left in British politics is axiomatically less sleazy or corrupt than the Right. I realise that many readers will regard it as a category error to describe such New Labour stalwarts as Stephen Byers and Geoff Hoon as men of the Left, but the fact remains that it was only Labour MPs who have fallen for the Sunday Times' latest undercover scheme to lure greedy politicians into offering to sell influence for cash.

I would be fascinated to know if it could also be demonstrated that Labour MPs are less generous to charity than the supposedly hard-hearted, tight-fisted Tories. I suspect that they are, if we as a nation are anything like our American cousins. A few years ago a professor at Syracuse University, Arthur Brooks, made something of a splash with a paper called "Who Really Cares: The Surprising Truth About Compassionate Conservatism". Brooks, who is not himself a Republican, found that Republicans gave more time to charities than Democrats – and even gave more blood. He also discovered that in the 10 states of the Union which voted most overwhelmingly for George Bush in the 2004 Presidential election, the average percentage of income donated to charity was 3.5, while in the 10 states where John Kerry did best, the average donated to charity was just 1.9 per cent of income.

Most strikingly of all, Professor Brooks claimed that "although liberal families' incomes average 6 per cent higher than conservative families, conservative-headed households give, on average, 30 per cent more to charity". As one startled American commentator remarked on Brooks' findings: "The belief that liberals care more about the poor may scratch a partisan or ideological itch, but the facts are hostile witnesses."

It's true that statistics are notoriously easy to manipulate, and in any event it can not be the case that all "liberals" are of one type of personality and all "conservatives" of another, whether for better or worse. There are near-saints, and appalling sinners, on both sides of the political divide, and always will be.

The most illuminating insight into the phenomenon of what is sometimes termed "private vice and public virtue" was put to me by Virginia Utley, who had been a secretary to a number of MPs over many years. She observed that those MPs who had the best public image as kind and caring were complete nightmares as employers, while those who had a public reputation as hard and unfeeling were absolute joys to work for. I called this Utley's Law, so successful was it in its predictive power.

Perhaps the findings of Professors Mazar and Zhong are no more than a further illustration of Utley's Law: that those who feel they have established a reputation (if only in their own mind) for virtuousness are capable of sinning without conscience thereafter, while those with least confidence in their own moral worth are the people who most merit our votes. The only problem is: how do we ever find out which are which?

d.lawson@independent.co.uk