A whistleblower has given WikiLeaks two CDs, reportedly containing the names of 2,000 Swiss bank clients who may have been evading taxes.

Swiss banker Rudolf Elmer worked for eight years in the Cayman Islands - a British overseas territory in the Caribbean.

Mr Elmer said he wanted the world to know the truth about money concealed in offshore accounts.

Mr Elmer handed over the data to WikiLeak's founder Julian Assange at the Frontline Club in London - the website's British HQ.

Mr Assange put in a rare appearance away from the remote country house, where he is living while he awaits extradition proceedings.

"I am here today to support him," Mr Assange told reporters.

"He is a whistleblower and he has important things to say."

The Australian said it would be weeks before any of the information could be checked and published on the WikiLeaks website.

Mr Elmer declined to give the names of those on the CDs or say how many individuals were involved.

"The only hope I have is to get society to know what's going on," he said.

"I have been there, I have done the job, I know what the day-to-day business is, I know how much is documented there and how much is not.

"I know how the system works. I want to let society know how this system works because it's damaging our society."

Mr Elmer was dismissed in 2002 after eight years as the chief operating officer of Julius Baer Bank in the Cayman Islands.

He is to appear before a Zurich court later this week to answer charges of bank secrecy violations, after he passed on clients' data to WikiLeaks in 2007.

The move led to tax evasion prosecutions in several countries against these clients.

AFP