The Electoral Commission is investigating "troubling" claims some voters cast more than one ballot at the General Election.
The watchdog said it had not discovered evidence of widespread abuse, but had received more than 1,000 emails from members of the public, as well as 38 letters from MPs, raising the issue.
The watchdog said it was working with police on how to investigate the claims.
It has also called for the Government to consider ways of reducing the risk of the rules being abused and for urgent action to tackle the number of duplicate applications by people who are not aware they are already registered.
Although some people, like students, can be registered in two areas, it is against the law to vote more than once in an election.
The Electoral Commission's report states: "Although people may lawfully be registered to vote in more than one place in certain circumstances, it is troubling that some voters appear to have admitted voting more than once at the General Election, which is an offence."
The watchdog said nearly two million young people applied to vote after Prime Minister Theresa May announced she would call a snap election.
About 500,000 more people were on the electoral roll for the 8 June poll than in 2015, taking the electorate to 46.8 million, its highest ever number.
A total of 2.9 million people attempted to register, with 96% applying online and 69%, 1.9 million, of those aged under 34.
Electoral registration officers say the numbers of applications from people who were already registered were high, ranging from an estimated 30% to 70% across the country.
Duplicate applications are not automatically detected because the information is held locally.
According to the watchdog, potential solutions include introducing a system to allow voters to check if they are already registered and adopting automatic registration schemes similar to those used in Australia.
Electoral Commission chairman Sir John Holmes said: "The size of the registered electorate for the General Election demonstrates the UK's strong tradition of democratic engagement, and reflects the hard work of all concerned.
"However, if we are to keep pace with modern habits and practice in a digital world, the electoral registration system must continue to evolve, and consider innovative solutions such as direct or automatic enrolment processes.
"These have the potential to deliver significant improvements to the accuracy and completeness of electoral registers as well as efficiencies for local authorities and the public purse."