British house prices increased by 5.5 percent last year, bringing the average price to 250,000 pounds (416,737 U.S. dollars) in December 2013, official figures showed on Tuesday. The Office for National Statistics (ONS) said average house prices increased by 0.9 percent between November and December last year. "House price growth is beginning to increase strongly across parts of the UK, with prices in London increasing at more than double the UK average," it said. London still led the country in house price with the growth rate standing at 12.3 percent last year. ONS figures also showed varied house prices between regions. Prices grew by 5.7 percent in England, 4.8 percent in Wales, 0.5 percent in Scotland and 4.8 percent in Northern Ireland. Annual house price increases in England were mainly driven by rises in London. A report issued by research body Ernst and Young Item Club issued early February warned that the housing market in London was beginning to show signs of bubble-like conditions, and asked the government to monitor the trend closely and be prepared to intervene. The forecast showed the average house prices in London were expected to reach nearly 600,000 pounds (980,000 U.S. dollars) by 2018, some 3.5 times the average price in Northern Ireland and more than 3.3 times the average in the North East. It said average house prices in Britain would grow by 8.4 percent this year and 7.3 percent in 2015, before cooling to around 5.5 percent in 2016. According to the ONS figures, prices paid by first-time buyers increased by 7.4 percent in December, higher on average than in December 2012. For owner-occupiers (existing owners), prices increased by 4.7 percent for the same period.