STATE-owned Irish Bank Resolution Corporation (IBRC), the former Anglo Irish Bank, has launched an appeal against the UK court ruling that found it acted illegally in forcing losses on "junior" bondholders.
In July the High Court in London found that "coercive" measures used in 2010 to persuade junior bondholders to accept losses on €1.6bn owed by Anglo Irish Bank were illegal.
IBRC filed court papers in London on Monday as the first stage in a Supreme Court challenge against the ruling.
The original case was taken by German investor Assenagon Asset Management. It had seen its €17m investment in Anglo's junior bonds wiped out by the 2010 deal.
The case has potentially significant consequences for all the bailed out Irish banks that used similar measures to ensure that subordinated bondholders incurred losses when the state shouldered the cost of rescuing them.
The July ruling has left the Irish banks facing potentially large compensation bills, possibly running into billions of euro, if the ruling is allowed to stand.
The case is being heard in London because the contracts for Anglo's bond were governed by English law.