Making use of new powers for opposition parties to demand such probes, parliament is due to call several high-profile figures to testify on Hypo's spectacular rise, near-collapse and role in increasing state debt and the budget deficit.

Former Hypo state commissioners Sabine Kanduth-Kristen and Angelika Schlögel are testifying on Wednesday. 

The Green Party has complained that most of the documents submitted for the hearing have not been adequately prepared for perusal. 

Opposition politicians have also criticised the fact that some of the files have been classified as secret and that some witnesses are allowed to remain anonymous. 

The most prominent witnesses are due to appear in a few weeks time,  including top current and former government officials in Austria and the German state of Bavaria.

Parliament president Doris Bures has emphasised that the hearing is not a tribunal but rather an attempt to get to the bottom of political responsibility. Finance ministers from the conservative People's Party (ÖVP) were in charge when Hypo was nationalised in 2009.

Austria bought Hypo from German lender BayernLB to avoid a collapse that would have sent shock waves through the region a year after Lehman Brothers went bust.

Hypo has cost Austrian taxpayers €5.5 billion ($6.46 billion), with billions more to come as "bad bank" Heta winds down assets left after Hypo sold its Balkans and domestic units.