Investigators for the US Congress are set to deliver a 100-page report today, which will accuse UBS and Liechtenstein's LGT Group of helping US clients avoid billions in tax through the use of banking secrecy laws.

The report is understood to contain details of how the banks 'colluded' with their clients, helping them to obscure their income from regulators. The banks are believed to have known of their clients' intent to hide their wealth from the Internal Revenue Service.

The methods used to hide client money included holding wealth in the name of a foundation, as well as counsel on the use of offshore structures and 'transfer corporations' which disguised movement and transfer through LGT accounts, the FT reported.

The report – which does not draw on any conclusion as to whether the banks broke the law – comes amidst an international crackdown on wealthy individuals who seek to hide their incomes in highly protected banking jurisdictions such as Liechtenstein.

It also suggests that the US Treasury loses $100bn (£50bn) annually to offshore abuses.

Further reading:

Liechtenstein on charm offensive

Ex-UBS employee says bank helped clients hide millions

UBS banker to plead guilty in evasion case