Vodafone ramped up the pressure in its appeal against a $2.9bn (£1.8bn) tax bill in India yesterday, signalling that it will take the country's government to international arbitration.
Its Dutch subsidiary has issued a notice of dispute against the Indians, saying the 2012 Finance Bill violated legal protections and harmed international investors.
Vodafone's case dates back to its takeover of Hutchison Essar in 2007. However, the company claims the new finance bill has implications for a wide range of Indian and international businesses in the country.
It also said the bill countermanded the Indian Supreme Court's ruling which decided it had no liability for withholding taxes on the takeover.