Morgan Stanley’s planned acquisition of discount brokerage E*Trade is facing an investigation by a law firm assessing whether the deal was undervalued.

Last month, the two companies signed a definitive agreement under which Morgan Stanley would acquire E*Trade for $13 billion in an all-stock deal, the largest deal by a major U.S. bank since the 2008-2009 financial crisis.

But the law firm of Kahn Swick & Foti released an investor alert on Wednesday, writing that “shareholders of E*Trade will receive only 1.0432 shares of Morgan Stanley for each share of E*Trade that they own.”

“KSF is seeking to determine whether this consideration and the process that led to it are adequate, or whether the consideration undervalues [E*Trade],” the law firm says.

If the acquisition goes through, it will give Morgan Stanley a foothold across all channels — financial advisory, self-directed and workplace — and immediate access to mass affluent investors, which the wirehouse has been increasingly courting.

The combined platforms would have $3.1 trillion in client assets, 8.2 million in retail client relationships and accounts and 4.6 million in stock plan participants, the companies said when the deal was announced in February.

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