"So the potential is that there may have been 500 duplicated, that's the worst case scenario, but we're only aware of nine that have been received so far out of the almost 14,000 sent out."
He said the situation would not invalidate the byelection or the elector's vote.
"If people have received two duplicate forms they should use one to vote with and just rip the other one up," Mr Ofsoske said.
He said there was no chance of people being able to vote twice if they received duplicate forms. Voting forms have a specific barcode and once scanned a second barcode with identical features would not be recognised by the electronic system.
How the error happened, and exactly how many duplicate forms were sent out, is being investigated.