The volume of deposits at the Irish banks which were covered by the Government guarantee scheme fell by €2.8 billion during May.
Figures from the Department of Finance show €700m of the €2.8 billion fall was accounted for by a weakening of sterling against the euro.
This reduced the euro value of deposits denominated in sterling by 2% during the month.
The Department said €300m worth of deposits had also been "reclassified".
Overall the levels of deposits - which comprise retail, corporate and deposits from non-bank financial institutions - is almost flat compared to May 2012.
When the impact of sterling and the reclassification of some deposits is excluded the total of €150.7 billion is €100m higher than in the same month last year.
The Department said the rate of growth in deposits had "moderated". It attributes this to the Irish banks being in a better position to fund themselves resulting in a "low interest rate environment" which is less attracive for savers.
It said the ending of the Eligible Liabilities Guarantee (ELG), or government guarantee, in the last week of March had made an "insignificant impact on deposit volumes in the covered banks".
In addition the Department has published figures showing Irish banks have reduced their dependence on funding from the European Central Bank by €3.9 billion or just under 10% in May.
Borrowing from the ECB has fallen by €29.1 billion, or 45%, to €35.6 billion.