With Revenue and Customs paying an informant to expose secret accounts in the Liechtenstein tax haven, it might seem that the war on tax avoidance is gearing up.

But even if this results in recouping some of the £100m in back taxes owed by the super-rich it is still a flea-bite considering that a TUC study a month ago found tax avoidance by Britain's biggest companies and wealthiest individuals now amounts to £25bn a year. The Tax Justice Network has also recently documented that the wealthiest people in the world hold a staggering $11.5 trillions of assets in tax havens.

But what is novel in Britain is the way that wealth and power over the last decade have been consolidated in a tiny new class at the top. They are epitomised by the egregious earnings of Stephen Schwarzman, chief executive of Blackstone private equity, who took home £200m last year (£3.85m a week). But that is only the extreme example of a new hyper-wealthy elite marked not only by extravagance of personal consumption, but also by a hold on economic and political power rarely if ever equalled in the past.

Britain now has five distinct classes. The poor, conventionally defined as those with less than 60% of median earnings, have to get by on less than £217 a week. But included with them should be the 1.5m people whose household incomes are no more than £10 above that, and constantly afflicted by insecurity.

Next come the largest class, those around the median income in Britain today of £23,600 (or £454 a week). This embraces a wide range of occupations from sales assistants and retail check-out (£240 a week), through nursing assistants, secretarial, security work, plant and machine operatives, electrical and construction, civil service executive grades, sales reps, to nursing, police and fire service (around £520 a week). Mostly they are secure, though at the lower end they remain vulnerable to economic downturns or if housing equity turns negative, as it may well be about to do for several tens of thousands.

Then comes the comfortably off managerial and professional class. Middle class is now too diffuse a term to be accurately descriptive, and would now be seen as including many in the previous category. But the professional-managerial class includes those in teaching, health and engineering (from £650 a week), through marketing and sales managers, production managers, up to corporate and senior management (around £1,670 a week).

In the higher reaches of the income scale there has always been a rich class, which might be arbitrarily defined as the top 5%. Numbering 1.4m, their income, according to the latest official Survey of Personal Incomes, averages £96,000 a year, with average investment income on top of that of £12,400 (totalling therefore £2,085 a week). Some might think, however, that the real rich category is confined to a much smaller group, say the top 1%. Their average earned income is now £220,000 a year plus £35,200 investment income, so they take home just over £4,900 a week.

However, a wholly distinct class has now developed at the very top end of the income scale which is entirely separate in the influence it wields through being embedded in the power structure at the highest levels. Even this class, tiny though it is, contains a vast range. At its lower end it starts from the top 0.1%, numbering just under 30,000 persons, each with an average earned income of £754,000 plus £146,000 investment income a year (just over £17,300 a week). It then rises into the stratosphere. The latest annual survey of the chief executives of the top 100 FTSE companies shows them taking home on average £2.8m a year (£53,485 a week). But that is only the average in these ultra-select and powerful groups. The top end, represented by the £27m (£519,230 a week) paid to Bob Diamond of Barclays Capital, is seen by many as greed incorporated when living in the same society are those on a minimum wage of £198 a week. A ratio between top and bottom incomes, which was less than 50:1 only 30 years ago, has now risen to 2,620:1.

What is even more striking is that these Babylonian excesses are now locked in more closely than ever to the exercise of power. In the last few years this has been exemplified by the rise of private equity. Buying up large public companies with huge debt leverage, selling off the property portfolio to transfer the debt to the company, and cutting costs via large-scale redundancies is the economic and personal price paid by others to secure the 2% annual management fee plus 20% of the profits for the private equity partners under the so-called "carried interest" system from which they can extract £20m or more apiece.

There are countless illustrations of this intertwining of wealth and power at the highest levels. The taper relief loophole by which top executives pay tax at a lower rate than their office cleaners was closed in 2003, but private equity was uniquely given exemption by the government. Sir Ronald Cohen, a guru of private equity, remains a close friend of Gordon Brown, who has also just appointed Damon Buffini, boss of Permira which recently loaded AA and Debenhams with huge debts and job losses, to his new Business Council of Britain.

The indefensible non-domicile tax loophole, which benefits some 60,000 hyper-rich individuals with personal fortunes reckoned to total £126bn, has only survived intensive lobbying against it in the past because its beneficiaries persuaded Brown as Chancellor that the privileges of the City must be protected at all costs. And the storm over cash for peerages further exposes just how far wealth now suborns the governing process in the hope of underhand reciprocal gain.

There is now increasingly a consensus, even among the well-off, that these excesses of power and wealth have gone too far. There is even a substantial degree of cross-party support in the Commons that the tax asylum seekers slipping through the net via non-domicile tax status should be brought to book by ending this loophole. The Treasury Select Committee recently reported that the taper relief concession for private equity buccaneers should be modified and "carried interest" treated for tax purposes as the income it clearly is. As the credit crunch consequences bite ever deeper into the incomes, not only of the poorer half of the population, but also of not-so-wealthy Middle England, the cry against greed incorporated will get a lot louder.