Although the words "means-test" may have few connotations for many people today, to some they conjure images of scroungers, or government inspectors snooping on people's income.

And the loathing with which the concept was once held may go some way to explain the objections to the policy many - including Labour backbenchers - have been expressing.

The issue may seem liable only to cause a bout of chin scratching at a think-tank dinner. But it in fact goes to the heart of society's priorities for having a welfare state at all.

On the one hand, it was long an aim of the cradle-to-grave nature of the welfare state that benefits should be universal. People should not lose their entitlement to benefits just because they had carefully saved all their spare pennies over the years.

Disabled groups have lobbied hard against means-testing

Some say means-tests dissuade people from saving or using their initiative. Others claim they give incentives to fiddle the system, and some say they create poverty traps where the poor stand to lose money by trying to earn more or save.

But on the other hand, when resources are scarce, who needs benefits most? Shouldn't those in greatest need be first in line for getting them? And if there is a limited pot of money available, the poor can get more help if those who don't need it aren't given it. Redistribution of wealth aside, it's a question of mere efficiency, its backers claim.

The symbolism of a new means-test being introduced by a Labour government is one that is not wasted on the policy's critics.

Target the most needy

The new measures would mean that people on incapacity benefit who also had an occupational or personal private pension would be means tested. They would start to lose their benefit when their pension gives them £5,964 a year, and lose it completely when they receive £9,300.

Social Security Secretary Alistair Darling said the point of the benefit was to replace income for people who could not work any more. "Given the fact that nearly half the people on incapacity benefit with occupational pensions are in the top 40% of the income bracket, it is only right that they should make a contribution to it," he said.

The government says three times as many people are claiming invalidity benefit as did in 1980, and it wants to limit the bill. Many older men are thought to be claiming it instead of unemployment benefit.

Previous governments have tried to address the question of means-tests by, for example, introducing taxes on benefits - designed only to hit those who can afford it.

Tide is turning

But Mr Blair's government, which promised to "think the unthinkable" on welfare reform, seems to have decided that means-tests are the lesser of the evils in addressing the problem of a huge welfare bill.

The invalidity benefit move is not alone - the means-test tide is coming in.