At least one Wall Street analyst is doubting the "long-term viability" of E*Trade Financial ( ETFC).

Citigroup analyst Keith Walsh expressed the concerns regarding the beleaguered online broker in an industry note in which he initiated coverage on E*Trade and two rivals, Charles Schwab ( SCHW) and TD Ameritrade ( AMTD) .

Despite earnings headwinds created by the weak equity markets, slowing trading activity and contracting interest spreads, Walsh gave Schwab a buy rating and TD Ameritrade a hold rating. But Walsh slapped a sell rating on E*Trade.

"On the one hand, E*Trade's retail brokerage operation is steady," Walsh writes in a note Wednesday. "The institutional business, however, remains an albatross as a result of its $25.5 billion loan portfolio. While we believe current management is doing all they can to address the company's legacy balance sheet issues, the long-term viability of the company remains in doubt, in our view."

In the final months of last year, investors became worried that the New York firm would not receive approval for a federal investment via the Troubled Assets Relief Program, or TARP. E*Trade filed an application for $800 million in funds in early November and has said publicly that it is "optimistic" of a TARP approval but still -- four months later -- no approval has been made.

The government's double investments in Citigroup ( C) and Bank of America ( BAC) suggest that both financial institutions are deemed too big to fail, but E*Trade seems to have been left in the dust. Some 450 banks and financial institutions deemed 'bank holding companies' received federal funds through the TARP initiative. And now some banks are even deciding that they don't want to deal with restrictions that come with TARP and have decided to give back the money.

If you liked this article you might like

Your Face Holds the Key to Apple Pay on the iPhone X

Massachusetts Opens Inquiry Into 7 Brokerage Firms

Apple's iPhone Sparked Monumental Changes in How We Trade Stocks