MADRID — For Gonzalo López, 77, it has been a lifetime of scrimping on a factory worker’s salary, trying to save enough to make sure his brain-damaged son would be cared for even after he was gone.

He and his wife put aside $87,000. But four years ago, as the economic crisis took hold here, a bank official called Mr. López at home to suggest he move his money into a new “product” that would give him a 7 percent return.

“I asked, ‘Is this safe?’ ” Mr. López said. “I trusted him. He knew the money was for my son.”

Today, Mr. López is one of about 300,000 Spaniards who, in the midst of a brutal recession, have seen their life savings virtually wiped out in what critics call a deceptive and possibly fraudulent sales campaign by banks that were threatened by the implosion of Spain’s property market. Many, like Mr. López, are older and lack formal education, and were easily misled when bank officials hit on the idea of raising capital and cleaning debts off their books by getting people with savings accounts to invest in their banks instead.

For many of these savers, the first hint of trouble — and understanding that they had bought into risky investments — was when some of these banks essentially failed about two years ago. Overnight, they were unable to withdraw their money.