"This could turn into another UBS situation. I foresee more fines and settlements being agreed in coming months," said David Treitel, tax director at consultant US Tax & Financial Services. He referred to the letter sent to the Swiss authorities from James Cole, the US deputy attorney general last week, requesting details of accounts from 10 Swiss banks. 

The deputy attorney set the short deadline of Tuesday 6 September or risk legal proceedings, according to The Daily Telegraph, citing Swiss newspapers the SonntagsZeitung and NZZ yesterday.

Swiss sources were quoted as saying that US clients holding accounts worth at least $50,000 between 2002 and 2010 are involved, and that the banks on the hitlist include Credit Suisse, Julius Baer, and some cantonal banks. 

Julius Baer declined to comment; Credit Suisse did not immediately respond to enquiries from this publication. 

If the legal threats are acted upon, it would hark back to 2009 when criminal and civil charges were levied against UBS. The outcome was an unprecedented $780 million settlement by Switzerland's largest bank and the surrender of details of around 5,000 client accounts. 

Treitel added: "This appears to be the US government applying scare tactics to individuals and institutions with the objective of raising more revenue ahead of the deadline for the Offshore Voluntary Disclosure Initiative. But there is a risk that if the US is overly aggressive through FATCA , it could trigger substantial capital flight out of America."

Others agree that the US has turned up the heat on Swiss banks and Switzerland could be in trouble. Lawyer Philip Marcovici told this publication: "It is clear that the US is very, very serious about its objective to stamp out tax evasion through reliance on bank secrecy centres such as Switzerland. But this has been clear for many years, and one must ask whether the Swiss have really been strategic in their approach to dealing with a more transparent world. In this poker game, the US seems to certainly have the stronger hand."

A number of countries aside from the US have been applying pressure to Switzerland to force the country to bend its centuries-old banking secrecy laws. As massive debt continues to weigh on the fragile recovery of the global economy, cash-strapped governments like Germany and UK have been pushing the Alpine state to surrender details on alleged tax evaders.

Just this morning came reports that hundreds of UK private client customers of HSBC are being investigated by HM Revenue & Customs in relation to hiding money in offshore Swiss bank accounts. The HMRC are reportedly analysing the records of 7,000 customers stolen by a former member of the Swiss bank’s staff, according to UK media. 

“HSBC does not condone tax evasion and seeks to comply with the letter and spirit of the law in all the countries and territories in which it operates,” a spokesperson for the bank said.

Meanwhile, last month the UK and Swiss governments signed an agreement that holders of offshore accounts in the Alpine state will pay a one-off charge of between 19 and 34 per cent of funds to settle old tax bills. As part of the agreement and as a “gesture of good faith”, Swiss banks will pay the UK an up-front sum of SFr500 million . It was similar to a deal inked by Switzerland in Germany a few weeks ago.