When Halliburton moved its headquarters from Houston to Dubai last year, the oil services group provoked a political storm. Despite assurances that the company was not seeking to avoid tax or scrutiny, the move was lambasted by Democrats as an example of corporate greed. Senator Hillary Clinton led the attack, denouncing the move as "disgraceful".

On the other side of the Atlantic, the spotlight is also on corporate defections after two big UK companies said last month they were shifting to Ireland for tax reasons. Others have also hinted at leaving. When United Business Media, a trade publisher, announced the move of its headquarters to Ireland, Vince Cable, the Liberal Democrats' Treasury affairs spokesman, criticised this as "blatant tax avoidance".