Disgraced former UBS banker Bradley Birkenfeld was sentenced to 40 months in prison for helping rich US citizens dodge their taxes. Now he is hoping for a bit more - a few billion dollars more, according to the New York Times.

As part of a deal with federal prosecutors, Mr Birkenfeld admitted to, among other things, helping to smuggle diamonds in a tube of toothpaste, the newspaper said.

Now, as thousands of individuals seek amnesty for keeping illicit, offshore bank accounts, Mr Birkenfeld and his lawyers hope to use a new federal whistle-blower law to claim a multi-billion dollar reward from the US government. It would be the largest reward of its kind if the request is successful, the report said.

The report highlights how tax authorities are being faced with the need to use the "carrot" of such payouts as well as the "stick" of threatened jail terms to encourage people to come forward over the issue of alleged tax evasion. 

Mr Birkenfeld, who is to begin his prison term as soon as January, is being represented by the executive director of the National Whistleblowers Center, Stephen Kohn. Mr Kohn successfully represented Linda Tripp, who helped expose the Monica Lewinsky scandal of the Clinton years.

“We are seeking at least several billion dollars,” Mr Kohn is quoted to have said.

The Birkenfeld case helped pave the way for a settlement under which UBS agreed to pay $780 million to the US authorities to settle criminal charges of enabling tax evasion; the bank is also, under an agreement between the Swiss and US governments, handing over up to 4,450 account-holder names to the US authorities. The affair has led to a historic breach of Swiss bank secrecy law and cast a shadow over the Alpine state’s banking sector, which contributes about 13 per cent of Swiss GDP.