The document said that "a break-up of European monetary union, especially in the transition phase, cannot be excluded as a possibility", and that the costs of remaining in it could be too heavy for some countries to bear.
The report by Norbert Berthold, a professor at Germany's University of Wurzburg, warned that member states were not immune from speculative attacks. Although they could not force a country out of EMU, it "might voluntarily decide to leave the system, as the cost of staying inside EMU for example, due to further rising unemployment, become too large to bear".
The report - not an official IMF document - added that the "primacy of politics over economics" in the decision to launch the euro in January "could have serious consequences concerning the stability of EMU in the transition phase" before notes and coins are issued in 2002.
Nick Herbert, chief executive of anti-euro group Business for Sterling, said: "This is further support for Britain's decision to remain outside the eurozone, at the very least until we have clearer evidence of whether EMU is sustainable."
But the rival Britain In Europe group, endorsed by Tony Blair last week, said the report was written by eurosceptics and insisted the findings were not endorsed by the IMF but merely published on its website as a contribution to the debate.
The group said it shared the views of Francis Maude, the shadow Chancellor, who told BBC Television yesterday the euro would probably succeed. Although a collapse was a possibility because of the "risks and strains" built into the system, Mr Maude said: "I think the likelihood is that the euro will survive, but that won't make the case for Britain joining it."
Thirty leading British businessmen yesterday promised Mr Blair their full support in the Britain In Europe campaign. They included the chairman of Ford, Ian McAllister; the chief executive of Rentokil International, Sir Clive Thompson; the restaurateur, Sir Terence Conran; the chairman of Nestle,Peter Blackburn; and the chief executive of Vodaphone Airtouch, Chris Gent.
They said in a joint statement: "A decision to rule out the option of membership even if it was in our national interest to join... would be deeply damaging to British business. [It] would jeopardise inward investment, put British businesses at a competitive disadvantage, and risk Britain's position in the single market."Reuse content