LONDON, August 9 - For a man who vowed to free Britain for good from its boom-and-bust economic cycle, Britain's Chancellor of the Exchequer Gordon Brown must be becoming increasingly twitchy over the ailing world economy. For after nine years of uninterrupted economic growth, Britain's economy is slowing fast and the risk of a quarterly fall in output is growing, threatening the ruling Labour's party's hard-won reputation for economic competence. As storm clouds gather over the world economy, Britain is starting to feel the chill and many economists, surprised by last week's quarter point rate cut, are pencilling in a further cut to protect economic growth. "There is a possibility, with the weakening of the service sector, that gross domestic product (GDP) could actually fall in the third quarter...we think interest rates are set to fall to 4.5 percent (from 5.0 percent)," said Jonathan Loynes, chief UK economist at Capital Economics. Rate cut talk sparked sharp gains on short-sterling futures on Thursday, a market which bets on the course of interest rates. The December 2001 contract stood at 95.200, suggesting a further quarter point cut in rates by the end of the year. The Bank of England issued a gloomy snapshot of the economy on Wednesday, forecasting economic growth would slow to just 2.0 percent this year -- below average growth in Britain over the past four decades of around 2.3 percent. The Treasury (finance ministry) has forecast growth between 2.25 and 2.75 percent.