Wall believes a negative rate could be "self-defeating," noting that while central banks haven't used it broadly, the experience in Denmark, one of the few countries to implement it, was unsuccessful.
The ECB is considering broader easing measures as Europe's economic recovery has been bedeviled in part by a strong euro keeping inflation at worryingly low levels and damping exports. Annual inflation in the 18-member euro zone picked up slightly in April to 0.7 percent, but remains way off the ECB's target of close to 2 percent. Risk aversion has made banks unwilling to lend, which has also weighed on the economy.
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But when Denmark implemented the policy, banks were unwilling to pass the negative deposit rate to their customers, squeezing their margins, Wall noted. At the same time, to deal with the added expense, some banks increased their lending rates, which was counterproductive to the central bank's objectives, he said.
In addition, negative deposit rates might also counter-intuitively strengthen, rather than weaken, the euro, if it encourages investors to move toward peripheral-country investments to pick up yield spread, he said.
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"That could attract capital flows in from outside the eurozone to take advantage of that, which might frustrate the objective of weakening the currency," Wall said.
Deutsche Bank isn't alone in doubting the effectiveness of a negative deposit rate.
"We are not convinced by the merits of a negative deposit rate, particularly given that it is unclear what this move is trying to achieve" ANZ said in a note Tuesday.