If that's the case then because the company made more profit after tax than they would have, had they been based in the US, it is good that UK tax payers invest in them because when they get their dividends or sell their shares/units they pay UK tax - tax the exchequer wouldn't otherwise receive.

Blairmore Holdings is, I understand, based in Ireland - if David Cameron still owned the units he previously owned would it be right to criticise him for doing so?  Of course revenue for the Exchequer would be lower because the company will be paying tax in Ireland before dividends are paid.

What it all seems to boil down to is where the tax eventually gets paid not whether or not tax is actually paid - unless of course the income is hidden but that would be tax evasion not avoidance.  The other problem I can see is regarding money laundering - low regulation must help in illegitimate funds being injected into companies.