Jokes about offshore tax havens with more mailboxes than people are plentiful in the world's onshore financial centres. But it looks as if the jesters have got it wrong: the real offshore tax havens may be the UK, the US and other supposedly "onshore" financial centres. These countries need to practise what they preach on reducing tax -avoidance.

A report out today points to the widespread failure of large countries to adhere to the tax rules that they have previously laid down for the havens. It brings into question what is really offshore.