Permanent TSB will this week announce plans to raise up to €550m from private investors.
According to The Sunday Business Post, the bank will use the cash to plug a capital shortfall after it failed the European stress tests last October.
The Government, which owns 99% of the bank, is not expected to take part in the fundraising and in doing so will see its stake fall.
PTSB was bailed out with €2.7bn of taxpayers' money.