Newly-registered voters and those abandoned by their previous party hold the power to swing 71 constituencies in England and Wales, the Bureau Local can reveal.

Our analysis has uncovered new battlegrounds in seats with large numbers of voters without a known party affiliation – new voters and 2015 voters whose party is not standing a candidate this time around.

Nearly 50,000 (49,984) newly-registered voters and 400,000 (395,672) former UKIP and Green supporters have been identified as key to constituencies where the margin is tight.

The seats are spread across England and Wales and include the fiercely contested battlegrounds of Derby North and Croydon Central, while also identifying others previously thought safe such as Colchester.

New voter power

The analysis has found 50,000 new voters in 19 seats where the increase in voter registration is greater than the majority won by the victorious candidate in the last election.

Less than 7,000 of these newly-registered voters have the power to swing six key Conservative seats: Derby North, Thurrock, Croydon Central, Twickenham, Plymouth Sutton & Devonport, and Crewe & Nantwich.

If Theresa May loses six seats without winning any new ones, she will no longer have a parliamentary majority.

Three further Tory-controlled seats - Colchester, Telford and Bedford - also have more new voters than the margin.

However these are seats where UKIP had a candidate running in 2015 but does not this time - and the number of people who voted UKIP last time outweighs the newly-registered voters.