GENEVA — Former UBS banker Bradley Birkenfeld hit out on Saturday against the "corrupt" US judiciary which sent him to jail even though he was the whistleblower who led to the US tax fraud case against the bank.

"The Department of Justice's corruption is evident today -- why am I the only one in prison when I had revealed everything?" the US banker asked in a French-language interview with Swiss newspaper Le Temps.

Birkenfeld turned in thousands of people for trying to evade taxes in the United States. But he was sentenced in August 2009 to three years and four months in jail for inciting UBS clients to commit tax fraud.

Martin Liechti, who headed the bank's wealth management service in the Americas, was detained by US authorities, but later allowed to return to Switzerland.

Birkenfeld claimed that officials had allowed Liechti to get away as he knew too much about high-profile clients of the bank.

"Why did they let Martin Liechti go?" he asked.

"Martin Liechti knew all the big clients. He knows the secrets that the Bush administration did not want revealed. They made an arrangement to allow him to leave for Switzerland where no one would be able to interrogate him," claimed Birkenfeld.

He charged that the fact that the Department of Justice failed to uncover the tax fraud without his help showed that it was "not only incompetent, but corrupt."

He also claimed that UBS' senior management was well aware that bankers were helping rich Americans to evade taxes illegally.

"Of course they knew. All these trips, the encrypted laptops -- the management knew all that, and had even authorized them.

"Denying it is just like saying that the Japanese generals did not know that an attack on Pearl Harbor was being prepared," he charged.

When contacted by AFP, UBS declined to comment on the interview.

Birkenfeld's revelations about the bank had led to US tax authorities' offensive against UBS in 2008. In a prosecution through US courts, the bank was forced to hand over 300 client names and pay a 780-million-dollar fine.

US tax authorities subsequently threatened the Swiss bank, which by then was struggling to survive the global financial crisis, with more litigation over another 52,000 suspected tax evaders.

The lawsuit was averted after the Swiss government intervened to negotiate a settlement with Washington, fearing that further damage to Switzerland's then biggest bank could have undermined its whole banking system.