Do we live in an age of hatred? Or has the language of political insult simply become more extreme? Tap the words “I hate Gordon Brown” into Google, and it comes up with 1,490,000 entries. David Cameron rates 611,000, Nick Clegg is well behind on 167,000 and Alex Salmond limps in on 71,000.

The internet does, of course, encourage extreme reaction - or perhaps just the reaction of extremists - but some of the online comments made about public figures today are the kind you might once have expected to see confined to the mad threats of a serial killer. I would like to think that these electronic ramblings are simply a safety valve for lunatics, but the explicitly personal insult is not confined to internet sites. There is a quality of venom about political commentary on both sides of the Atlantic that seems out of proportion to the performances of those on the receiving end, and cannot wholly be explained by the febrile climate of the times.

Mr Brown is now the object of what can only be described as a feeding frenzy that goes well beyond criticism of his political indecision, the handling of the Northern Rock affair and the errors he admits to, such as the 10p tax fiasco. It is fuelled too by party infighting and the paying off of ancient scores; given the long-running rivalry between him and Tony Blair, and the opportunity for John Prescott, Cherie Blair and the oleaginous Lord Levy to sell their memoirs on the back of it, the resulting bitterness should not surprise us. But none of that quite explains the personal vitriol.

Here is one sentence, culled from a recent national newspaper leader (OK, the Daily Express, which some might argue scarcely qualifies for the name): “They [British voters] know their Premier to be a neurotic, dysfunctional mediocrity; an insecure Stalinist who worships power but cannot take a decision; a moral and political coward who tries to fill the vacuum at the heart of his leadership with blustering rhetoric and adolescent bullying.”

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Elsewhere, the barely concealed suggestions that Mr Brown is psychologically flawed, even autistic, possibly mad, that he cannot communicate, is hopelessly insecure, an inept loner incapable of running his own life let alone that of the nation, is the regular stuff of Tory attacks. In their intensity and their personal character, they are surely unprecedented in postwar politics.

North of the Border, Mr Brown's colleague, Wendy Alexander, leader of the Scottish Labour Party, is subject to the same hysterical reaction. She too has been guilty of poor judgment and some rash policy statements that she has lived to regret. But it is now routine to describe her as “unstable,” “neurotic” and - yes, that word again - “mad”.

In America, the extremism is, if anything worse, with both Barack Obama and Hillary Clinton the object of ferocious criticism. Mrs Clinton's policies may be anathema to Republicans, and even to some Democrats, but the dislike she engenders goes well beyond the purely political. Those who have referred to her over the past few months as a “monster,” “evil”, “sinister,” “the bitch” “deceitful” and “congenital liar” appear to be suggesting that she has personal flaws that damage her not just as a candidate for the presidency but as a human being.

She is not the first presidential candidate to have veered occasionally from the truth, but is she uniquely dishonest, or does she attract added hostility simply because she is a woman - and a Clinton? How ironic that the wife of the man who first coined the phrase “the politics of personal destruction” should now be the victim of it.

The language used against Mr Obama is less overt, but just as deadly. The implication that behind the charm and the eloquence stands a man who hates America, is secretly a Muslim and therefore dangerous to the security of the nation, is rarely spelt out openly, but it hovers between the lines of right-wing commentary, and barely conceals the streak of racism that runs through it. If he wins the nomination, this is the theme that will be peddled with ever-greater ferocity by his opponents.

Where does all this come from? Nothing in the personal qualities of political figures of the day, however deficient they may be, justifies this level of abuse. Lampooned figures in the past - Harold Wilson, Edward Heath, Jim Callaghan and John Major among them - were, from time to time, enveloped in crises every bit as damaging as those that confront Mr Brown. But never were they subjected to such woundingly ad hominem attacks.

It could be that our society feels more threatened than it used to, that we seek to pin the blame for our own insecurity on the failures of our leaders. But are they as uniquely inefficient or even deranged as we seem to suggest? And are we really more prone to fear than we were in the days when nuclear attacks threatened and the Cold War enveloped us?

The more likely truth is that we live in a society that has thrown off many of the constraints that once governed public life, and where personal abuse has become a routine part not just of politics but of sport, entertainment and journalism. It may be that we are compensating for the culture of deference that marked us in the past; but if that is so, we have gone well over the top. Hatred is a strong word. It should be reserved for our real enemies, not imagined ones. Used too often, and too lightly, it ceases to have any meaning.

We should also remember that these political figures are also human beings. I cannot imagine what Mr Brown - to say nothing of Mrs Brown - feels when he reads the daily litany of insults delivered to his door. I imagine he suffers.

“If you prick us, do we not bleed?” asked Shylock; even prime ministers, I guess, have feelings. The time has come to add a new dimension to public life, one that might counterbalance the present vogue for all-out aggression. We could call it something dramatically new. What about the politics of compassion?

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