They are a staple of consumer-complaint hot lines and Web sites: anguished tales about money stolen electronically from bank accounts, about unhelpful bank tellers and, finally, about unreimbursed losses.

But surely customers of the elite private banking operation at JPMorgan Chase, serving only the bank’s wealthiest clients, are safe from such problems, right?

Wrong, says Guy Wyser-Pratte, an activist investor on Wall Street for more than 40 years who uses his hedge fund’s war chest of roughly $500 million to wage takeover fights and proxy battles in the United States and Europe.

In May, Wyser-Pratte learned that someone had siphoned nearly $300,000 from his personal account at the private bank through many small electronic transfers over a 15-month period.

Then he was told by the bank that he could stop the theft only by closing his account and opening a new one — an enormous hassle, he said. And finally, JPMorgan Chase told him that the bank would cover only $50,000 of his losses.

“While this is an unfortunate situation, we believe our response has been entirely appropriate,” said Mary Sedarat, a spokeswoman for the private banking service at JPMorgan Chase.

Wyser-Pratte emphatically disagrees. “They never should have approved that first transfer,” he said.

The wealthy financier “is getting a taste of what the rest of us have to deal with all the time,” said Gail Hillebrand, the senior staff lawyer for Consumers Union in San Francisco.

That sour taste is called automated clearing house fraud, theft involving unauthorized electronic transfers through the automated networks of the circulatory systems that connect the world’s bank accounts.

When a consumer writes a check, the merchant that accepts it is entitled to have the specified amount taken from the customer’s bank account and sent electronically to the merchant’s account.

But once someone has certain routing numbers for a customer’s account, fraudulent transfers become possible unless the customer carefully scrutinizes all of the transactions on the monthly account statement.

If the consumer reports a clearly unauthorized transaction within 60 days, federal banking rules require the bank to cover the loss. Hillebrand said. If not, and if the bank informed the customer in advance about the 60-day deadline, the bank has no liability.

Consumer advocates agree that online purchases and automatic bill-paying arrangements have greatly complicated the task of catching fraudulent transfers — particularly small ones — from busy accounts.

And Wyser-Pratte’s personal account was as busy as his life. Louis Morin Jr., his chief operating officer, said his boss splits his time between Paris and New York and travels almost constantly. “He is not someone who writes 30 checks a month — more like thousands a month,” Morin said.

And a retail bank statement is kindergarten arithmetic compared with the monthly statement for a private banking client. Indeed, Wyser-Pratte said that the statements had become so complicated not even a Wall Street veteran like himself could detect the continuing theft.

“I kept complaining that the bank’s records showed I was overdrawn when I shouldn’t be,” he said. Each time, he was assured that the statement was accurate, even if he could not decipher it.

As for the 60-day deadline for reporting a theft, “I never knew about it,” he said. “I opened that account eons ago, it must be 20 or 25 years now. I don’t think I ever signed anything agreeing to that policy.”

Wyser-Pratte has filed a complaint with the New York City Police Department. A detective working on the case confirmed that an investigation was under way.

According to Morin, the money was sucked out of Wyser-Pratte’s personal account through dozens of unauthorized purchases of computer equipment from Dell. But so far, police investigators have been able to trace only a single $1,600 shipment of equipment, delivered to a nonexistent business in Brooklyn.

Wyser-Pratte, understandably anxious to solve the mystery, complained that neither Dell nor his bankers were giving the police enough help.

“Dell is cooperating fully” with the police, said Jess Blackburn, a company spokesman. “We have been very responsive to all requests for information.”

JPMorgan Chase is also cooperating fully, said Sedarat, the bank spokeswoman. “This is an important reminder that clients are responsible for monitoring activity in their accounts.”