Plymouth City Council says more than 850 students and young people have been 'incorrectly' added to the electoral register.
The council has written to 247 under-18s in the Plymouth Sutton and Devonport constituency who have been sent polling cards despite being under age.
Additionally, 635 students are on the register without having filled in an 'invitation to register' form.
The council says it is writing to everyone affected to say they have been removed from the list, and if they believe they are eligible to vote they must re-register.
READ MORE: The West Country Battlegrounds READ MORE: GE 2019: All the candidates standing in the West Country
Following the last General Election in 2017, council chiefs apologised after more than 1,500 postal ballots went missing in the run-up to polling day, while many people were turned away from polling stations and 6,000 votes were not counted on the night.
Then in the 2019 local election, the council admitted adding 304 students to the register without them confirming an application.
Plymouth Sutton and Devonport have a Conservative and Labour battle with the Tories winning the last election.
Labour won this target marginal seat which was high on their list in 2017 and remains so in this election.
ITV News West Country has spoken to one Plymouth resident who says his 17-year-old stepdaughter was sent a polling card.
KEY DATES FOR 2019 ELECTION:
Deadline for receiving applications for registration: Tuesday 26th November
Deadline for receiving new postal vote and postal proxy applications, and for changes to existing postal or proxy votes: Tuesday 26th November
POLLING DAY: Thursday 12th December, 07:00-22:00