George Bush is a stronger believer in income equality than Gordon Brown.
These figures (pdf) from the CBO (via Greg Mankiw and the Kruse Kronicle) show that the poorest fifth of Americans paid an average of 4.3% of their income in federal taxes whilst the richest fifth paid 25.5%.
How do these figures compare to the UK? Table 16A here gives the answer. The poorest quintile in the UK paid 36.5% of their income in tax, whilst the richest fifth actually paid less - 35.5%.
Britain's tax system, then, is regressive whilst the US's is progressive.
You might object that I'm not comparing like with like. I'm including indirect taxes, whilst the US figures exclude local sales taxes (though they include excise duties).
However, if we look only at income tax and national insurance, the UK system is still less progressive than the US's, at the federal level. The bottom fifth pay 6.2% in direct tax (net of credits) whilst the top fifth pay 23.7%. The ratio of these tax rates is 3.8, compared to 5.9 for the US federal tax takes.
If you don't believe these figures, check out Willem Buiter's calculations that top marginal taxes are higher in New York than London.
Sure, you can quibble with these numbers. The US figures exclude local income taxes. And perhaps the UK taxes the poor more because they have more income thanks to more generous welfare benefits.
But however you slice it, the message seems to be that the UK's tax system after eight years of "Labour" government (my figures refer to 2005-06) is less progressive than the US's federal tax system after years of pro-rich Bush presidency.