AEC officials allowed 75 voters at a northern suburbs retirement home to cast their ballots for WA's $20 million Senate re-run election into a faultily constructed ballot box.
The AEC has this morning declared those votes invalid and will allow the electors to cast new ballots.
After The West Australian revealed details of the irregularity today, the AEC told candidates by email this morning it would seek to send a mobile team out to the RAAFA Estate in Merriwa to take the votes again as soon as possible.
"An AEC mobile polling team attended the residential aged care facility on Monday 31 March 2014 and identified that there was a problem with the construction of the ballot box in its possession," AEC Acting Electoral Officer Kathy Mitchell told candidates this morning. "The team applied a temporary solution however, the container used was later found to be not fully secure in accordance with the requirements of the Commonwealth Electoral Act 1918.
"The AEC has since obtained legal advice about this matter, and those affected voters are considered to have not voted in this election. Accordingly, the AEC is able to remedy this situation and protect the franchise of those voters by enabling them to validly cast their vote.
"The AEC will make arrangements for a mobile team to visit to assist the affected voters as soon as practicable.
"The AEC's prime concern is naturally to protect the franchise of the residents affected.
"The AEC apologises for any inconvenience to the residents, candidates and others affected by this event."
West Australians are going back to the polls this week because the AEC lost 1735 votes after the original September 2013 poll.
At one point, the result of a recount at that election turned on the preference distribution of just 14 votes.
The Liberal Party said the AEC still had plenty of questions to answer over the affair, including whether its workers had been sufficiently trained to avoid a repeat on Saturday.
"The Australian Electoral Commission incident with unsecured ballot papers is a serious issue," the party said in a statement.
"The Liberal Party is pleased that the affected people will be allowed to re-cast their vote.
"If this problem occurs again on Saturday - this remedy will not be available.
"This calls into sharp focus the need for better training of AEC staff and better management.
"This incident occurred on Monday, it is Thursday today. The Liberal Party became aware of an issue on Tuesday and sort urgent clarification.
"The Liberal Party, along with outer parties, has only today been informed officially by the AEC today.
Palmer United Party leader Clive Palmer said the AEC had failed again.
"I am bitterly disappointed 75 ballots have allegedly been placed in an unsecured box at an AEC polling station," Mr Palmer said.
"This indicates the AEC has not got its act together and signals great concerns for the integrity of the WA Senate re-election.
"None of the irregularities with the voting system that I have highlighted in recent months have been remedied for this election.
"Despite the resignation of the Electoral Commissioner and the AEC Manager for WA over the lost votes debacle during the WA Senate recount, and despite the investigation and condemnation of every political leader in the nation, the AEC has still not learned its lesson.
"I predict there is worse to come in this weekend's election."