Nearly 14 million voters are in seats that have not changed hands since the Second World War, a study has found.

Almost 200 constituencies in the Commons have not changed allegiance since 1945, with the average seat in the UK having been won by the same political party for 42 years, analysis by the Electoral Reform Society shows.

The data also highlights one in 10 of the 650 seats in the Commons - 54 Conservative and 11 Labour - have not swapped colour since 1918, with some having not changed since the 19th century.

Just 70 seats, 11% of the total amount, transferred to a different party at the last General Election in 2016.

YouGov's MRP projection predicts 58 seats will change hands in the upcoming vote on December 12.

The Electoral Reform Society's research shows across the last three General Elections, an average of 99 seats changed hands each time, representing 15% of seats switching colour.

According to the analysis, 192 constituencies have not changed hands since 1945 or earlier, affecting 13.7 million potential voters in the upcoming election if the trend continues.

Former prime minister Theresa May and ex-transport secretary Chris Grayling's seats in Maidenhead and Epsom and Ewell respectively have been held by the Tories since 1874.

The analysis also shows the Tories have held seats for the most amount of time on average at 47 years, with Labour close behind at 45 years.

Constituencies in the Labour heartlands of the north-east of England and the Conservative "safe seats" of the south-east were found to be the least likely to change hands, with the average transitions 63 and 76 years respectively.

The average number of years since Liberal Democrat seats changed hands was much lower at eight years.

The research has taken into account equivalent predecessor seats where boundary and name changes have been made and did not include seats that have changed hands due to an MP defecting to another side.

Dr Jess Garland, director of policy and research for the Electoral Reform Society, said: "We've heard often that politics is volatile and anything could happen in the coming election but even so, hundreds of seats across the country haven't changed party hands for decades.

"Huge parts of this country are effectively competition-free zones, with 'safe' seats leaving voters demoralised and ignored time and again.

"As our research shows, seats representing nearly 14 million voters have not seen party change in a lifetime and dozens more seats have not seen change in a century.

"Elections under Westminster's broken system rely on a handful of 'battleground' seats, while many areas barely have a contest at all."

Darren Hughes, chief executive of the Electoral Reform Society, said the 2019 General Election should be the last to be conducted under the first past the post voting system.

He said: "Even in landslide years where the balance of power in Westminster has flipped millions of people in these 'shoo-in seats' see the same party colours representing them in Parliament.

"Being trapped with the same representation for decades is not the hallmark of a responsive and functioning democracy.

"With trust in politics at rock bottom and people desperately wanting to be heard, it's vital we bring our democratic structures into the 21st century.

"This election should be the last ever conducted under the rotten first past the post system that has shut so many voices out."