The UK's electoral registers are the foundation for our democracy; they are the basis on which people can cast their vote. No matter how strong your views, if you are not on the electoral register, you won't be able to vote. So, the completeness and accuracy of these registers is central to the health of the system as a whole.

Despite their significance, our long-standing programme of research at the Electoral Commission has consistently shown that millions of people are incorrectly registered to vote or missing from the registers. Last week we published our latest research, which showed that up to eight million people are not correctly registered, or not registered at all. This is more than the combined adult population of Scotland and Wales, and would be equivalent in number to more than 100 UK Parliament constituencies.

We know that not everyone wants to participate in elections. But these numbers are a consequence of an outdated registration system that disproportionately affects young people and private renters.

It's not just voters that are affected by an inefficient voter registration system, but also electoral administrators. Registering to vote is currently heavily event-based, which means Electoral Registration Officers (EROs) have to use their limited resources and capacity at the most critical time ahead of elections to manage high numbers of applications to register to vote. Recent reforms to the annual canvass have helped to alleviate some of the burdens, but the process still struggles to capture population movement or identify 16-and-17-year-olds who are newly eligible to register.

Electoral Registration Officers work hard to ensure the registers are as accurate and complete as possible. But governments have not yet given them access to the tools and data they need to make significant and sustained improvements to the registers. Without legislative change, there is a limit to what EROs and others across the electoral community can do to try and improve the health of our registers.

We need a clear plan to ensure that electoral registration processes are modernised. As part of this plan, the UK, Scottish and Welsh governments should pass legislation that creates clear legal gateways for government departments and public sector bodies to share data on potentially eligible voters with EROs. This can enable EROs to register them to vote directly, or to send them targeted invitations to register. The Welsh Government has already highlighted its intention to work with local authorities to design and pilot automatic voter registration for devolved elections.

We have spoken to several UK Government departments, public bodies, universities and tenancy deposit schemes about whether and how data could be used to improve the accuracy and completeness of electoral registers. Automatic and integrated voter registration are already the norm in many countries and we see this within the UK as well. For example, Cardiff University and Cardiff City Council already work together on an integrated electoral registration model so that students are asked if they want to register to vote as part of the online process for student enrolment. We believe that registering to vote could be integrated within other public service transactions – for example, a similar prompt could be asked of drivers when they apply for a driver's licence or to change their address with DVLA.

Making electoral registration more joined-up with other public services and citizen transactions raises important questions on data sharing and cyber security. There are already security measures in place to improve the robustness and security of the electoral registration service, and we have recommended that the UK Government develops the existing Individual Electoral Registration service to support secure and efficient data sharing between data source organisation and EROs, to enable modern registration processes to be delivered.

Electoral administrators are delivering well run elections under increasing pressure and capacity constraints. But we know that the system is hindering their efforts and leading to millions of people missing or incorrectly registered. Our evidence continues to highlight the need to develop new approaches to electoral registration that can bring long-term improvements. These will require governments to change the law. We are ready to play our part alongside the UK's governments and electoral administrators to improve the system.

Phil Thompson is head of research, Electoral Commission