An influential committee of MPs has warned of "obstacles" to British membership of the European single currency.

In a report published today, the Commons Treasury select committee also said that if Britain rules out membership then a "window of opportunity" to influence the workings of the European Central Bank could close.

The cross-party committee of MPs said that proposed changes to the ECB ahead of the expansion of the European Union to central and eastern Europe would weaken Britain's influence if it joined. The changes mean that Britain would have no say in one in five interest rate-setting decisions - although the same rotational system would also apply to France, Germany, Italy and Spain.

A YouGov poll for today's Telegraph finds that 62 per cent of Britons would vote against joining the single currency if a referendum were to be held during the next few months while just 28 per cent would vote in favour.

Meanwhile, Tony Blair has told the FT that joining the euro is "in the country's interests".