WHAT'S 'fair'? Well, it's a concept that is horribly abused. Almost everybody seems to be complaining that they are the victims of some gross injustice, showing little sense of what fairness really means.

It could be Michael Caine crying out that it's not fair that he has to pay a 50 pence tax rate to keep some layabout in bed. Or it could be working-class voters tempted to vote for the far right BNP political party because they are outraged so many immigrants allegedly have automatic access to schools, housing and hospitals for which they haven't paid. Oh, it's all so unfair.

To those who believe fairness is a liberal value, here it is being hijacked against progressive taxation on the one hand and reasonable immigration on the other. Meanwhile, the UK government is so blind to the popular ideal of fairness that it tried to stop Gurkhas who had fought for Britain from settling here.

What is fair is difficult territory. Too many on the left assume that preferences for more equity and proportionality are so widely shared that support for liberal policies is semi-automatic. Higher rates of income tax for the better-off, an Equality Bill or making public services available to everyone on the basis of need are so self-evidently the right thing to do that the mass of popular opinion will rally to one's side.

But it doesn't — and it won't. Fairness can be used to justify any position on the political spectrum. One of the reasons the UK's ruling New Labour party is facing a rout at the next general election is that it has not managed to build a consensus over what is fair.

Fairness, I think, has four dimensions and none of them is automatically liberal-left territory. There is the fairness of equity, so embedded in our DNA that four-year-olds protest at the lack of justice in not being treated as well as their brothers and sisters. There is the fairness of need I should be helped or compensated for the bad luck of life. So if I am born into a poor family, suffer heart disease or am thrown out of my job for no fault of my own I deserve your support.

There is the fairness of efficiency and merit I worked really hard to get this job and I do it well; it is only fair that I should be paid more than you. The economy needs me to be given that incentive because such an expenditure of effort needs to be fairly rewarded. Lastly, there is the fairness of proportionality I can be paid more than you for doing the same job because I am more productive.

This is a political minefield and unless parties of the left walk carefully, they soon find that ideas of fairness are deployed against them. And the UK's New Labour has believed in the political value of ambiguity. Thus it can appease the tabloid press without being accused of inconsistency. Now the party and wider society are suffering the consequences. The BNP's position is that Britain should be for the British and British means being white. Even if it formally repudiates racism, its core philosophy is about identity politics, which it masks by appeals to fairness.

As former New Labour minister Margaret Hodge says about potential BNP voters in her Dagenham (east London) constituency, what tempts them to vote far right is not racism, but unfairness. If economic migrants were welcomed but had to wait for a phased period before they could claim the full array of benefits, as the British journalist and editor of Prospect magazine David Goodhart has proposed, the excuse of unfair abuse would be lifted. All that would remain would be racism.

Meanwhile, Michael Caine should feel embarrassed about his remark. I am sure if he were asked whether it was fair for the rich to contribute more to the public purse in times of need, the fishmarket porter's son would answer yes, along with the overwhelming majority of Britons. In the same way, even BNP voters would endorse the overwhelming majority view that Gurkhas should have the right to live in Britain, complete with unqualified access to public services. That is the proportionate and equitable bargain, given their willingness to fight and die for Britain.

What provides the opening to Caine and the BNP is being able to jump, with too little challenge, to a different context in which one fairness principle can trump another. Keep out immigrants who haven't paid for public services! Proportionality trumps need.

People hate cheats, even while they consistently vote in hypothetical tests in favour of assuring the disadvantaged a surprisingly high basic income. They will support the unemployed, but only if they are unemployed through no fault of their own.

Blair did try to make access to benefits tougher for perceived cheats, but he never did it as part of a wider quest for fairness. Rather, it was sold as a social crackdown. Equally, he tried to toughen the rules on immigration, but not in the name of fairness, rather in the cause of keeping foreigners out to appease the right-of-centre press.

His successor as premier, Gordon Brown, is no more secure about fairness, for all his anxiety to present himself as its champion. If he understood the proportionality principle better, he would be more willing to clamp down on bankers' bonuses. Equally, if he understood how ready people are to pay for generous benefits as long as there is tough action on cheats, he could have reshaped the benefits system. And a politician who understood equity could never have made such a mistake over the Gurkhas.

— The Guardian, London