Ministers are facing further pressure over the controversial dropping of a fraud probe into a £40 billion arms deal.
The Liberal Democrats are set to table a motion in Parliament calling for the publication of a key report into the Al Yamamah contract with Saudi Arabia.
The National Audit Office compiled the document after scrutinising the original BAe Systems deal, which was signed in 1988.
However, it remains the only NAO report never to have been put into the public domain, according to party leader Sir Menzies Campbell.
He said: "Parliament is entitled to see any report commissioned in its name. There is no reason why this report should be treated any differently."
Sir Menzies also called for Prime Minister Tony Blair to make a statement to the House before it rises for Christmas on why the Serious Fraud Office probe had been halted.
"Conflicting versions from the Prime Minister, the Attorney General and the head of the Serious Fraud Office need clarification," he added.
The Government announced on Thursday that the SFO investigation was being abandoned, citing the vital importance of good diplomatic relations with the Arab state. The decision led to claims that ministers had bowed to political pressure.
It was reported that the Saudis had been threatening to withdraw vital intelligence on al Qaida operatives, as well as ditching commitments to buy 72 jets from BAE Systems.
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Anti-trade campaigners are expected to deliver an ultimatum to the Government that they must either reinstate the inquiry within two weeks or face a high court challenge.
