NEW YORK — Susan Bernardo trusted her stockbroker. She wound up losing a fortune.

Her broker, David Harris, advised her to sell $400,000 worth of relatively safe municipal bonds, she says, and sink the proceeds into real estate and energy partnerships in hopes of earning more. She had received the money from a settlement after her husband died in an accident and needed it to raise her son.

More than six years later, those investments are in trouble. The stream of interest payments she used for living expenses has mostly dried up and the value of her portfolio is half of what it was, according to a financial planner who helped her file a claim against the broker.

Bernardo says Harris never told her how risky the new investments were, or about the fat 5 percent commission that brokers typically get selling them. Harris hasn’t returned calls seeking comment.

That her broker might not have acted in her best interest never occurred to her, until recently.

“I thought, ‘OK, someone is watching over me,”’ says Bernardo of Wantagh, N.Y. “Maybe I was naive.”

The Obama administration thinks too many brokers aren’t looking out for their clients and instead pushing risky and costly investments in a rush for big commissions. The White House is backing a proposed rule it hopes will help end the practice. The new rule would require brokers handling retirement accounts to put the interest of their clients ahead of their own, a so-called fiduciary standard long required of lawyers, doctors and some financial professionals.

Under the current rule, brokers must limit their recommendations to what is “suitable” for clients based on their financial situation and appetite for risk.

That’s too weak, critics say. Brokers don’t have to offer cheaper alternatives or keep an eye on the investments. Critics say this current rule has allowed brokers to invest too much of their clients’ money in high-fee mutual funds that erode returns over the years, or put it in risky products that can wallop them with losses.

In announcing its support for stricter standards, the White House cited a report from its Council of Economic Advisers that estimates brokers with conflicts of interest are cutting returns in individual retirement accounts by 1 percent a year, or about $17 billion.

And if brokers were held to the same standard as doctors or lawyers, critics say, fewer would be cleared of wrongdoing by the Financial Industry Regulatory Authority, or FINRA, an industry-funded group that oversees arbitrations and can impose fines and other penalties.

More than six of 10 FINRA arbitrations last year resulted in no award for investors, though many cases were withdrawn or settled before a ruling.

“When they give bad, conflicted advice, they should be held liable, and they’re not,” says Mercer Bullard, a law professor at the University of Mississippi. “Unless they’re a fiduciary, it’s very difficult to win that case.”