The SNP demanded an inquiry today after it emerged that a record of everyone who voted in last year's Glenrothes by-election has gone missing.
The party had asked to see the marked registers from November's crucial by-election - which resulted in a shock victory for Labour.
Lindsay Roy held the seat - which is next door to Prime Minister Gordon Brown's Kirkcaldy and Cowdenbeath constituency - despite predictions that the Nationalists would win it.
The marked registers reveal exactly who voted in the by-election, as officials cross out the names of individuals who turn up at the polling station to cast their ballot.
However Nationalists were told last week that this had gone missing from Kirkcaldy Sheriff Court.
A spokesman for the Scottish Court Service confirmed that the registers had been delivered to the sheriff clerk there, but added that "comprehensive searches" had failed to find them.
And he said an investigation into their loss was being carried out.
But Tricia Marwick, the SNP MSP for Central Fife, called for an independent inquiry.
She said: "The marked registers are an essential element of any election campaign. They allow a check of who voted, but not how they voted, to confirm that the election was conducted properly.
"Without these records there is no evidence of either a fair or unfair election and that undermines the confidence of everyone who took part."
She went on: "It is almost beyond belief that a by-election which attracted media coverage throughout the UK, which delivered a surprise result and had a much higher turnout than anticipated now has no records to show who actually voted."
The Nationalist demanded: "There now needs to be the fullest independent inquiry carried out."
She suggested that either the Electoral Commission or the Sheriff Principal for the area could carry out an inquiry.
The SNP convener for the Central Fife area, John Beare, asked to see the marked registers in November, but it was the end of January before the Nationalists were told they were missing.
A spokesman for the Scottish Court Service said: "Despite comprehensive searches for this document, we have been unable to locate the marked register requested within Kirkcaldy Sheriff Court.
"We can confirm that the Sheriff Clerk at Kirkcaldy Sheriff Court took receipt of these items following the Glenrothes by-election in November and that the voting papers for this election, which were deposited at the same time, are available.
"This is deeply regrettable and we are investigating the circumstances relating to this loss."
But a Scottish Labour spokesman accused the Nationalists of "sour grapes"
The spokesman described the loss of the registers as "clearly very worrying" and said Holyrood justice secretary Kenny MacAskill should "carry out an investigation into why an SNP government department has lost confidential personal data again".
But the spokesman hit out: "It's like an extreme case of sour grapes and dirty tricks rolled into one.
"Lindsay Roy won the by-election because of the incompetence of the SNP locally and nationally. The ballot papers were counted fair and square in front of the eyes of the world."
He added: "Ms Marwick's comments are an insult to the intelligence of Fifers. She simply cannot accept that they decided to vote for Labour, not her party.
"The marked register is provided for the convenience of political parties. The people have spoken, and the SNP must accept they lost. Fife voted for Labour and as a result Lindsay Roy is now a brilliant local MP."Reuse content