MP Michael Dugher has urged people to check they are registered to vote following changes to the registration process.
Under the Government's new system, between three and five per cent of voters who registered before could be deleted from the register this December.
This means around one million people could lose their right to vote.
Mr Dugher said: "Barnsley Council is working hard to ensure that people do not fall off the electoral register.
"I would urge local residents to complete the annual household canvass and make sure they are registered to vote online.
"This takes just five minutes and can be done on www.gov.uk/registertovote.”