A parliamentary investigation into the collapse of Credit Suisse will keep its files closed for 50 years, according to a parliamentary committee document, a level of secrecy that has triggered concern among Swiss historians.

The document means the investigating commission would hand over its files to the Swiss Federal Archives after a longer gap than the usual 30 years to ensure high levels of confidentiality apply to the investigation, which has generated huge public interest.

The investigation will focus on the activities of the Swiss government, financial regulator and central bank in the run up to the emergency takeover of Credit Suisse by UBS in March.