"We've found some credit unions failed to change the amounts on signs or some credit unions in remote shared locations were not properly serviced," said Otsuka of CUNA Mutual's Credit Union Protection Claims Division.

In a memo sent to state leagues this week, Otsuka wrote that Reg E requirements for disclosing ATM fees "has triggered a significant risk concern for credit unions" with lawsuits filed alleging violation of section 205.16 of the regulation, "which applies when a consumer initiates an electronic funds transfer or a balance inquiry at an ATM owned or operated by an institution that does not hold the account to or from which the transfer is made, or about which an inquiry is made."

CUNA Mutual said there are currently 35 of the lawsuits now open over the past several months with two or three law firms identified as lead plaintiffs.

"When credit unions charge a fee to a consumer using a non-credit union ATM network card or debit card, the regulation requires posting a sign in a prominent and conspicuous location on or at every ATM owned or operated by the credit union stating that a fee will or may apply," the statement said.

That means disclosing the fee on the terminal screen or on paper notice before the consumer is committed to paying the fee "but it is not necessary to include the amount of the fee on the sign," said Otuska, adding the class actions represent a fledgling cottage industry of law firms going after CUs "like ambulance chasers."