Ihara was named chair of the compensation committee and sits on the nominations committee.

He was named chair of the group in 2011 after a lengthy search for a replacement for Ratan Tata.

Former Finance Minister Sir Michael Cullen has already been named chair the group, whose first meeting is expected towards the end of next month.

The letter was also signed by Elizabeth Duke, a former Federal Reserve governor named chair of Wells Fargo's board last year in a broader overhaul.