Former Australian Federal Police chief Mick Keelty claims the result of next month's Senate election is open to corruption because polling booths are usually staffed by low-income earners.
Appearing before Federal Parliament's electoral matters committee, Mr Keelty said he still could not rule out criminality over how 1370 ballot papers vanished during the bungled re-count of the tight contest.
Mr Keelty, who was hired to investigate how the votes went missing, branded the conduct of last year's WA Senate election a "disaster" and was "relieved" the Electoral Commission WA manager Peter Kramer quit over the botched poll.
The debacle has forced WA back to the polls on April 5 for a re-run election estimated to cost taxpayers $23 million.
Mr Keelty made the suggestion that part-time electoral workers - many retirees and students - could be bribed to "foul up" an election outcome.
"Think about the people involved in this, we're talking about people who are low-income earners," he said. "I'm not being disparaging, but I'm saying the opportunity for something corrupt to happen is there.
"I had no evidence of corruption in here whatsoever, but the problem is I can't, hand on heart, stand here and say that didn't happen, because the system was so parlous."
Liberals yesterday seized on new shadow parliamentary secretary for WA Alannah MacTiernan's support for the mining tax.
The Perth MP said there were "strong arguments in favour of a profits tax", despite only a week earlier telling Labor MPs that they should not block abolishing the mining tax to revive the party's flagging brand in WA.
"Whether or not the formula is quite right . . . is certainly a subject of some discussion, but the idea of a profits-based tax is a sound one," she said.
But Liberal deputy leader and Curtin MP Julie Bishop said Ms MacTiernan had failed WA less than 24 hours into her new job.