Britain's economy grew by 0.5 percent in the third quarter, unrevised official data showed on Friday.

Gross domestic product expanded in the three months to the end of September but at a slower pace compared with growth of 0.7 percent in the second quarter, the Office for National Statistics said in a second estimate.

The data comes two days after the UK government said Britain's economy would grow far slower than expected next year as state borrowing jumps mainly as a result of a projected financial fallout from Brexit.

Analysts pointed to an economy intact since the June 23 referendum in favour of Britain exiting the European Union but warned of troubles ahead.

"This is a firm growth story that again shows the economy has weathered the Brexit storm very well so far," ING bank senior economist James Knightley said following Friday's GDP update. 

"The data flow so far suggests that the fourth quarter should also post a decent growth rate, but we still expect a substantial slowdown in 2017."

Brexit will spark an economic slowdown and ravage public finances, forcing a multi-billion-pound spike in state borrowing over the next five years, a gloomy government budget update revealed on Wednesday.