"These novel and unilateral theories of tax jurisdiction are both unprecedented and inconsistent with existing norms of international tax law and long-standing treaty commitments, " the groups argue in a letter to Algirdas Semeta, the EU tax commissioner.

CNN: US banks warn over planned EU 'Tobin tax'

On Sunday, Google's executive chairman Eric Schmidt defended his company, saying it had "always aspired to do the right thing", but added that "international tax law could almost certainly benefit from reform".

BBC: Apple 'among largest tax avoiders in US' - Senate committee

Kaplan is a shareholder of the international law firm of Greenberg Traurig LLP and chair of its New York tax department.

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