Sterling has lost ground after Mr Brown's statement, with market analysts believing that if it is to join the euro, it will be at a level weaker than its current rate.
Sterling fell in early trading after UK Treasury studies - published yesterday morning - suggested it would need to weaken substantially before euro entry. It later extended losses to 71.55 pence sterling per euro, down more than 1.5 per cent on the day.
A background study, published by the Treasury, said the pound's equilibrium rate was equivalent to 75-85 pence per euro, much lower than most analysts' forecasts of a likely euro entry rate.
The Treasury studies also said recent movements in the exchange rate and current accounts threw some doubt on the estimates at the lower end of the range, and that a new model gave a medium-term equilibrium exchange rate for sterling of 1.37, or around 73 pence per euro.