Vedanta Resources has named London-based arbitrator James Spigelman to represent its case in international arbitration involving tax demand of over Rs 20,495 crore on its unit, Cairn India. The government has named Donald McRae, a member of the UN International Law Commission, to defend itself in the arbitration initiated by the London-listed Vedanta under the India-UK Bilateral Investment Protection Treaty, sources said. The Singapore-based senior counsel and chartered arbitrator Michael Hawng will be the chairman and neutral judge of the three-member arbitration panel. In April 2014, Cairn India was slapped with a tax demand of Rs 20,495 crore for failing to deduct withholding tax on alleged capital gains made by its erstwhile parent company, Cairn Energy, in 2006-07 when it reorganised its India operations. The tax notice on Cairn India came three months after the Income-Tax Department issued a Rs 10,247-crore tax notice on Cairn Energy in January 2014 using a retrospective tax legislation.