Chancellor Gordon Brown has moved to reassure the pro-euro lobby he is prepared to back British membership of the European single currency when the economic conditions are right.

With Cabinet colleagues among those pressing him not to kick British membership into the long grass when he announces the Treasury's assessment of his famed five economic tests, Mr Brown sought to highlight his pro-Europe credentials.

But he reinforced the expectation he will say Britain is not yet ready for membership when he makes his long-awaited statement to the Commons - due by June 7 at the latest.

Mr Brown emphasised the importance of making significant progress on the "very big economic reform agenda ahead in Europe."

The Chancellor is under intense pressure from the euro's supporters to signal a negative assessment could be re-evaluated and a referendum of voters organised before the end of this parliament.

The pressure was increased by his Cabinet colleagues, Scottish Secretary Helen Liddell and Leader of the Commons John Reid.

Mr Reid insisted the Chancellor's announcement would be no more than a short-term conclusion as, in principle, the Government wanted to join the single currency.

Speaking on ITV1's Jonathan Dimbleby programme, Mr Reid said: "When that decision is taken in the course of the next few weeks, it will be announced and it will be a decision for the time being."

"It doesn't bind us for any specified period in advance because the decision we are taking is not whether we will join the euro but when we will join the euro."

Mrs Liddell told a Sunday newspaper the impact of staying outside the eurozone on Scotland's economy should be included in the Treasury's deliberations.

She said; "The consequences for Scotland are vitally important. We could have a situation in which 24 countries are in one currency and we are in another.

"That has implications for inward investment and jobs and we need to specify what that cost would be."

In his interview, Mr Brown said: "I have always been pro-Europe. And by history, by geography, by economics we are very much part of Europe.

"It would be entirely the wrong policy to take the Conservative Party's view on this issue. They would refuse to join the euro even if it was in the national economic interest to do so.

"That is to rule out the euro on grounds of dogma, something that is unacceptable to me."

Shadow chancellor Michael Howard claimed the Government was in a mess over the euro.

He said: "The Cabinet is at sixes and sevens over whether Britain should join the euro.

"It is quite clear their decision will be based not on what is best for Britain but on which faction gains the upper hand."

David Frost, director general of the British Chambers of Commerce, said: "Any euro verdict that can be reopened and reviewed within 12 to 18 months will be potentially destabilising and will lack credibility."

The chambers urged the Government to deliver its verdict on the five tests in a way that minimised uncertainty and made it easier for firms to plan ahead.