The figures in part mark a rebound from unusually weak growth in the second quarter, due to disruption from extra public holidays to mark a royal wedding, as well as from Japan's tsunami, which hit supply chains.
The Bank of England has forecast that the economy will stagnate in the last three months of this year, and grow at a n annual rate of just 0.7-0.8 per cent through most of 2012.
The Office for National Statistics confirmed that British gross domestic product grew by 0.5 per cent in the third quarter, and was up 0.5 per cent on the year, in line with a provision onal estimate earlier this month and with economists' forecasts.
This was the fastest pace of growth since the third quarter of 2010, but economists are unanimous that economic expansion is likely to slow rapidly, as Britain faces the headwinds of the euro zone debt crisis and ongoing government spending cuts.
Slow growth and unemployment at a 17-year high is increasing pressure on Chancellor George Osborne to announce measures to boost the economy in his autumn statement next w eek, but he is hamstrung by his tough deficit reduction targets.
Last month the Bank of England restarted its quantitative easing programme, authorising another 75 billion pounds of gilt purchases, and most economists expect it to endorse another round when the first purchases are complete in February.
The ONS said that inventory growth added 0.7 per cent to GDP on its own in the third quarter -- the largest contribution in a year. Household consumption was flat, but this still marked the first quarter that it had not fallen since quarter two 2010.