LONDON (AFX) - Britain could join the euro at an exchange rate less than 10 pct below its current level, the Financial Times reported citing independent City and academic economists. A survey of 20 economists by the Financial Times found that the average sustainable entry rate they proposed was 0.68 stg to the euro. That is roughly equivalent to 2.90 marks to the pound -- just 8.5 pct below Tuesday night's closing rate. The expectation that the pound would have to be devalued sharply if Britain were to join the euro has been seen as a significant obstacle to entry. Just a few years ago, many economists and businesses still expected the pound to drop back to about 2.50 marks Economic techniques for calculating equilibrium exchange rates or assessing purchasing power parity across countries suggest that the pound is significantly overvalued. However, faith in those techniques has been shaken by the British economy's strong performance, the newspaper said. "Over the past five years the exchange rate has been more stable than at any time since it was floated in the early 1970s," said Robert Barrie of Credit Suisse First Boston. "I don't see why it shouldn't be sustainable," he added. Since 1992, when 2.95 marks proved impossible to defend as the central rate in the exchange rate mechanism, the economy seems to have grown stronger relative to many other European countries, the newspaper said.