(Bloomberg) -- The lobby group that represents Deutsche Bank AG and Commerzbank AG pushed back against the prospect of an increase in the amount of money that lenders must park at the European Central Bank.

Raising such requirements would be equivalent to a tax, according to Heiner Herkenhoff, who heads the Association of German Banks. The step would dent earnings, constraining banks’ ability to pay higher interest to savers and their capacity to lend, he warned.

The ECB took banks by surprise in July with a decision to offer zero interest on their minimum reserves, rather than the 3.25% it had previously paid out. Some officials have since floated the idea of stricter requirements to tighten monetary policy and help them rein in inflation.

“Raising the reserve requirement would come at the wrong time and be counterproductive,” Herkenhoff said Tuesday, citing the need for credit to fund investments in Europe’s economy. The move would put the continent at a disadvantage to other jurisdictions, he said.

Lenders in the euro area will miss out on a combined €6.6 billion ($7 billion) of revenue over 12 months after the interest on reserves was eliminated this month, with German banks accounting for €1.8 billion of that, according to Herkenhoff.

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