Gordon Brown, the guardian of the government's five economic tests, has said the decision will be vital for the long term future of the UK.

Making his annual Mansion House address to City leaders, the chancellor said that "because of its constitutional significance as a decision...the economic benefits should be clear and unambiguous".

He said the impact of the housing market would also be considered, along with an analysis of national business cycles and exchange rates.

Brown hinted that taxes may have to be used to control economic demand if Britain joins the euro. "EMU membership would also place a greater premium on the success of domestic instruments of policy as an adjustment tool, in particular, fiscal policy and fiscal frameworks," he said.

The Mail's verdict is that he has toughened the criteria required to achieve a positive decision.