Annual savings rates on demand deposit accounts in the Post Office Savings Bank currently range from 0.10% to 1.5%. Retail banks jockeying for position as the bulk of SSIA accounts close down in April are offering rates up to 6% now that base interest rates have ticked up over the last 18 months.

"If you look at what we're offering, it puts us out of the running for SSIA money, " said an An Post spokesman.

"But we can't shift [the rates]." An Post acts as an agent for the NTMA, which is the borrowing agency for the government. The POSB acts as a mechanism for the government to raise money and the NTMA sets the rates. But as interest rates set by the European Central Bank dropped to record lows, the government has preferred the bond markets for its cash needs. Consequently, the NTMA hasn't responded to the recent rate changes as retail banks have.

An Post earns fees from the administration and management of the accounts, which have 6.7bn in funds on deposit, but it feels it could be squandering its brand on products that aren't doing much for customers.

This is one of the rationales behind An Post's 112m retail banking partnership with Fortis, which is scheduled to begin rolling out products this year.