Prime Minister Tony Abbott's plan to repeal the carbon and mining taxes may become a little harder to achieve after a fresh Senate election was ordered in Western Australia.
The Australian Electoral Commission successfully petitioned the High Court for the result to be declared void after 1375 WA Senate votes were lost during a recount after the September 2013 election.
Justice Kenneth Hayne said the missing votes meant he could not determine who was duly elected.
Mr Abbott will set the date of the election for the six seats which could prove crucial to his legislative plans.
If the Liberals pick up three seats, Labor wins two and the Greens take the final seat the government will be denied one of the cross-bench conservative votes it was hoping to secure in order to get its legislation through the upper house.
A recent survey in WA found 58 per cent of people would vote as they had done in 2013, but 13 per cent said they would change their vote and 29 per cent were unsure.
Opposition Leader Bill Shorten said the issues for the election were jobs, the future of the resources sector and preventing the Abbott government's cuts to health and education.
He also wants the government to release its initial national commission of audit report before the poll, so voters can get an idea of what might be cut in the federal budget.
Finance Minister Mathias Cormann said only the Liberals were committed to axing the mining and carbon taxes, which were damaging the WA economy.
"The Liberal party has a strong and experienced team which will deliver for Western Australia," he said.
There will be no restrictions on parties standing an entirely new list of candidates, but the major parties are not expected to do so.
The initial count last year declared the Liberals and Labor winners of the first four of six seats, with terms starting on July 1.
The final two seats went to Dio Wang of the Palmer United Party and Labor's Senator Louise Pratt.
But a recount narrowly gave the final two seats to the Australian Sports Party's Wayne Dropulich and the Greens' Senator Scott Ludlam.
Justice Hayne said Senator Ludlam and Mr Dropulich were not duly elected because the number of ballot papers lost far exceeded the margin between the candidates.
Mr Abbott will effectively set the new election date, but the election writ will be issued by WA Governor Malcolm McCusker with the poll following at least 33 days later.
Special Minister of State Michael Ronaldson said the AEC needed to ensure such a "failure of process" never occurred again.
AEC spokesman Phil Diak said the commission would put in place greater security measures for ballot papers and better training for officials ahead of the election.
He said the election would cost more than $13 million to run.
Mr Dropulich was disappointed with the court's decision, but he expected his party's primary vote to be higher than in 2013.
Senator Ludlam said the election was crucial.
"There is a balance-of-power Senate seat in play here," he said.