Britain's economy expanded last year less than first thought, official data revealed on Thursday, adding to concerns that Brexit uncertainty was impacting growth.

Gross domestic product growth stood at 1.7 percent in 2017, the Office for National Statistics said in a revised estimate.

The ONS originally had GDP growth at 1.8 percent last year, compared with 1.9 percent in 2016.

Last year's figure remains the lowest level of UK annual growth since 2012.

The ONS also revised down the estimate for growth in the final three months of 2017, saying that the UK economy expanded by 0.4 percent during the period, slower than an initial reading of 0.5 percent.

The data come one day after Britain revealed a first rise in its unemployment rate since late 2016.

"Higher inflation was the reason that we have not seen the UK's economy expanding more than the previous estimates," noted Naeem Aslam, analyst at Think Markets.

"Brexit is the biggest elephant in the room and this dominates all stories. The longer the uncertainty remains around this issue, the worst the effect... on the economy," he said.

British inflation meanwhile shot higher last year as a drop in the pound following the 2016 referendum vote in favour of the UK exiting the European Union resulted in higher import costs.