Permanent TSB is expected to announce plans this week to raise between €500m and €550m from private investors.
The State-owned bank will announce results on Wednesday, with an analyst conference call expected the following day during which management, including chief executive Jeremy Masding, is expected to provide further details.
It is expected that the State, which holds a 99pc stake in the bank, will not take part in the capital raise and will therefore see its shareholding diluted.
News of the amount to be raised was reported in 'The Sunday Business Post'. A spokesman for Permanent TSB declined to comment.
The bank must raise cash to meet European demands that it boost its finances by €855m after failing stress tests that assessed whether it could survive a new financial downturn.
The bulk of the amount to be found has already been accounted for, thanks in part to a €400m State loan and the positive impact of rising property prices and asset sales.
It had been expected the amount needed to be raised was in the region of €125m, but it is understood that the bank will use the additional funds sought to repay that €400m loan earlier than expected.
AIB, Bank of Ireland, Ulster Bank and the Irish wing of Merrill Lynch International were all given a clean bill of health.