The chancellor, Gordon Brown, last night doused hopes of early UK entry into the euro when he insisted that deep-seated Treasury doubts about the economics of monetary union would have to be overcome before Tony Blair could contemplate a referendum on the single currency.

In a speech seen as an attempt to counter the impression left by Mr Blair's address to the Labour party conference that an early plebiscite would be held by spring 2003, the chancellor said he would not "fudge or short-cut" the assessment.

Mr Brown told the CBI in Birmingham that the Treasury, which has grown increasingly concerned about the weakness of the euro and the performance of the European Central Bank since the single currency's launch in 1999, would take a "rigorous and comprehensive" look atthe five tests, based on extensive technical and preliminary work.

Sources said Mr Brown wanted to dispel the idea that the prime minister's speech a month ago meant the political decision to join the single currency had already been taken and meeting the five tests would be simply a rubber-stamping exercise.

Although the chancellor reiterated his support for the euro in principle, his speech made it clear there may be no referendum in this parliament.

Mr Blair, while noting in Brighton that the five tests were more than window dressing, had increased speculation that the government was committed to entry when he told the party conference he would hold a referendum in this parliament if the economic conditions were right.

Mr Brown's speech last night fleshed out the details of the preliminary