Gordon Brown's sacred five tests for guiding Britain's entry into the euro are effectively meaningless, said the Treasury official responsible for assessing Britain's suitability for the single currency.

Speaking to an audience of students before Christmas, Gus O'Donnell, the head of macro-economic policy and international finance at the Treasury, said that the final decision will be governed by politics as "economics can never be clear and unambiguous." Using slides and hand-drawn cartoons, O'Donnell went on to criticise the way the euro worked and cast doubt on whether 12 nations could maintain economic stability with individual tax rates but one interest rate.

Tony Blair meanwhile told reporters on the first day of his visit to south-east Asia that Britain would be "very foolish" to run away from the euro. He added that sceptics of the single currency were "hiding their hands in the sand" because the arrival of the notes and coins had made the single currency a reality.