Caerphilly Council is confident that postal votes are safe, after concerns were raised by residents unable to seal their envelopes.
The local authority has reassured residents that ballot papers are secure, despite admitting a manufacturing error, which has left a slit on some ballot paper envelopes.
Gwent Police said they were aware of the manufacturing error and will not be investigating it further.
However, Caerphilly residents have taken to social media to voice their concerns over the safety of their ballot paper.
Caerphilly resident, Stuart Roberts said that he knew several residents who had experience this problem.
He said: “None of us will be sending our ballots off as we are scared our vote will be switched.
“Everyone I personally know had a split envelope both online and those not on social media.
“Some were split on the left and some on the right so to say it’s a manufacturing fault is hard to believe.
“Yesterday the council were saying there was nothing wrong with ballots, today it’s a manufacturing fault.”
However, not all residents who submitted for postal votes have experienced the manufacturing error.
A council spokesman said: “The council is aware of concerns circulating on social media about a fault with the inner seal on some items of stationary being used for the return of postal votes.
“It has come to our attention that there is a minor issue with small batch of envelopes from our suppliers, but it is important to stress that this has no impact whatsoever on the integrity or security of the ballot process.
“When the postal vote is returned, this inner envelope is sealed within another outer envelope and is only opened in a secure environment in the presence of official observers and agents appointed by candidates.”