An Australian living overseas has revealed he was able to vote twice in the same-sex marriage postal survey thanks to a glitch.
James West, 35, formerly of Sydney, works as a journalist in New York and registered to vote in the plebiscite online from overseas.
He received a 'secure access code' allowing him to cast his vote, but at the same time received a letter in the post addressed to him with a different code.
Mr West told Daily Mail Australia being assigned two different codes immediately threw up a red flag.
After registering to vote online he was sent a letter from the Australian Bureau of Statistics on September 25.
He was concerned about what his experience meant for the integrity of the online voting system.
He got in touch with the ABS, and after a 'sizeable back and forth' was told that the bureau would 'clean this mess up later', and assured Mr West he had not voted twice.
He was also given a confusing explanation as to which one of his two votes would count.
At first he was told it would be the initial vote he had cast, but then the ABS said it would be the code that was generated most recently – in this case the one that he applied for online.
Mr West said the multiple-vote experience raised two 'major issues', and believes there should be more transparency about the process.
He also questioned whether the ABS was equipped to pull off the plebiscite.
'We really don't know much about what kind of software system they're using when they talk about duplicate votes.
He said he hadn't heard of any other ex-pats having similar experiences.
An Australian Bureau of Statistics spokeswoman said the bureau has measures in place to 'ensure the secrecy of each survey response and the integrity of the process'.
The spokeswoman said processing of forms means there is 'no risk' that people can vote twice.
'The ABS is carrying out the... survey with a high level of transparency and integrity to provide assurance in the accuracy of the data'.