Up to 1.7 million British homeowners - or one in seven - could owe more on their mortgages than their homes are worth within the next year if house prices continue to drop, a report from the world's leading credit rating agency Standard & Poor's warned Wednesday. Around 70,000 people are already in what is called negative equity as a result of the housing market falls, which have seen prices decline by 9 percent since last year. If house prices drop by a further 17 percent, Standard & Poor's estimates that that number will explode to 1.7 million people. Worryingly, the ratings agency also predicted in a separate report on Wednesday that the housing market would indeed plummet by 17 percent before "the trough of this cycle is reached in 2009." Credit analyst Andrew South said that "the downward trend in UK house prices now seems well established, and we expect prices to continue falling in the near term." If the prediction comes true, the fallout would be devastating. Rising interest rates as a result of the credit crunch mean that many people are already having trouble keeping up on their house payments.