Credit Suisse made false claims in US visa applications, conducted business with clients in secret elevators and shredded documents to help more than 22,000 American customers avoid US taxes, according to a scathing report by a US congressional committee.

Credit Suisse handed account statements to one client tucked inside a Sports Illustrated magazine as part of their “cloak and dagger tactics” according to Senator Carl Levin, chairman of the US Senate Permanent Subcommittee on Investigations which drafted the report. The bank also helped clients create offshore shell entities to avoid taxes and aided them in structuring transactions so they fell below the $10,000 amount that would alert the government, according to the report.

It said Credit Suisse created an office at Zurich airport where more than 10,000 US accounts were held, known by the code name SIO85. Bankers made 150 trips to the US from 2002 to 2008 to aid in the tax evasion efforts. At its peak, the assets of the more than 22,000 customers totalled as much as $12bn.