Campaigners have called for people to be automatically registered to vote to enable eight million more to take part in the next general election.

A new report commissioned by campaign group Unlock Democracy found as many as 1 in 7 UK citizens may not be properly registered to vote. That’s a figure equivalent to the populations of Belfast, Birmingham, Bristol, Cornwall, Derbyshire, Edinburgh, Essex, Glasgow, Greater Manchester, Leeds and Staffordshire combined.

Younger voters and voters from ethnic minorities and economically deprived communities are among the least likely to be registered, the report found. The report’s author, Professor Toby James of the University of East Anglia said: “Nearly one hundred years on from women winning an equal right to vote as men, it’s past time to make sure we’re registering every voter. Around the world countries are moving towards automatic registration – and it is now the UK’s turn.”

Just 71% of 18-34 year olds registered in Great Britain are registered to vote, compared to 96% of over 65s. As well as a notable disparity between urban and rural areas, there is a 30 percentage point gap between the proportion of private renters and the proportion of home owners on the register. London and the North West the regions with the lowest completeness levels.

Tom Brake, a former government minister and Director of Unlock Democracy, added: “Voter registration at the moment is much more complicated than it needs to be. With AVR, rather than having to send multiple reminders to potential voters, electoral authorities would be able to use existing data simply to verify and register these individuals automatically, saving both time and money.

“In view of Labour’s plans to lower the voting age, synchronising voter verification and registration with the point at which 16-year olds are issued with a national insurance number is just common sense.”