Number 10 has moved to dismiss claims that Gordon Brown's reluctance to support Britain's membership of the single currency will make the promised referendum very unlikely while he remains chancellor.

Roger Liddle, an adviser on European affairs to Tony Blair, yesterday told a meeting of executives and central bankers in London that "Britain's economic future is inextricably linked to Europe".

He added that: "It's obvious that Europe's single market is Britain's home market - any failure to achieve Europe's potential reduces Britain's potential."

Ed Balls, Gordon Brown's chief economic adviser, will tomorrow make a speech on the government's five tests for joining the single currency.

His speech, which has been organised by the Institute of Contemporary British History, is set to be more an academic lecture that will set the decision in its historical context than an indication of which way the government will go.

The Express reports that the prime minister is coming under pressure to appoint a new chancellor in any third term Labour government because of Gordon Brown's hostility to the single currency.