Lawyers for the Liberal Party say there is no reason for a fresh Senate poll in WA because only 23 of the 1370 missing ballot papers affected the outcome of the botched re-count.
In a submission to the High Court, sitting as the Court of Disputed Returns, the party's legal team argues the Australian Electoral Commission has "reliable evidence" from which it can determine the election result as if the ballot papers had not been lost.
The party's barristers, Stephen Donaghue and David Bennett, said it would not be "just" to order a fresh poll because it would invalidate the election of four senators who were properly elected. "A declaration that the election was absolutely void should be a remedy of last resort, to be ordered only where a reliable outcome cannot be determined in any other manner," the submission said.
Justice Kenneth Hayne will hold a two-day hearing next week in Melbourne on how to resolve the disputed election.
The Palmer United Party's Dio Wang and Labor Senator Louise Pratt were the original winners of the last two seats but a re-count gave them to the Australia Sports Party's Wayne Dropulich and Greens Senator Scott Ludlam.
The outcome hinged on the flow of preferences at a crucial elimination point when just a few votes separated the Australian Christian Party and Shooters and Fishers Party.
But the loss of 1370 ballot papers during the re-count led the AEC to request a fresh election because it had lost confidence in the result.
The Liberals say that officials had twice scrutinised the missing 1370 votes in the initial count, with records showing just 23 were relevant to the margin at the elimination point.
If these votes were admitted as evidence, it would put the Shooters and Fishers ahead by just one vote, enough to change the result and allow the court to declare Mr Wang and Senator Pratt the winners.