Most of the pensioners making these claims are foreigners who moved to Spain to spend their retirement years.
They are now accusing Nordea Bank and Danske Bank of fraud, providing false tax advice and of misleading marketing. These pensioners say that they have lost hundreds of thousands of euros in investments that their banks ensured them would generate no less than 7 percent gains.
They purchased an investment product which they also believed would allow them to avoid paying inheritance and wealth taxes in Spain.
The banks' advice has proven to be wrong and several of the customers have unwittingly violated Spanish tax laws.
The Chapmans, a British couple, transferred around 150,000 euros from another bank to Nordea. Soon afterwards, Nordea employees told the Chapmans of an excellent investment product offered to families and couples who own their own houses in Spain.
"My wife wasn't very interested in the investment because she thought that there had to be a catch. I thought that I'd trust this gentleman. He wouldn't do us any harm," explains Alan Chapman.
Now, Alan and Annette Chapman face the prospect of losing the home they bought with their lifesavings, as well as the rest of their assets. Dozens of more people are in a similar situation. They have started referring to these two Nordic financial institutions as "pillaging Vikings".
Nordea: We don't give tax advice
At the heart of this complex investment product is the idea that by refinancing their homes, these pensioners could create a tax plan. In fact, the mortgages were used for investment activities via Luxembourg, not for the real estate intended.
Nordea concedes that its clients have suffered large losses. According to the bank, this is, however, due to bad timing - the investments were made primarily just before a financial crisis started in 2007. According to Jonas Torp, the Head of Communication and Marketing for Nordea's Luxembourg operations, the bank did not give actual tax advice to its clients.
"We do not give tax advice. We are bankers, not accountants. But, of course matters related to taxation are one important part of many banking matters," says Torp.
Torp considers the investment losses "very regrettable", but also a risk that is always associated with investments.
Danske Bank, which has ended activities in Spain, declined to comment on the affair to Yle, as the cases are related to individual customer relations.