NEW YORK, May 4 Reuters The practice of short selling is coming under increased scrutiny as shares of regional banks remain under pressure, with some calls for more regulatory oversight of the practice.

Short sellers, who borrow shares they expect to fall and hope to repay the loan for less later to pocket the difference, have profited from the banking crisis. They gained 1.2 billion in the first two days of May, analytics firm Ortex said.

Wachtell, Lipton, Rosen Katz, a law firm that has represented large companies, such as Twitter, in mergers and against attacks from hedge funds, on Thursday called on U.S. securities regulators to restrict short sales of financial institutions.

In a letter to clients, Wachtell said that the Securities and Exchange Commission SEC should regulate what it defined as coordinated short attacks by imposing a 15trading day prohibition on short sales of financial institutions.

This would allow time for regulators to act and for investors to digest information, Wachtell39;s cochairman Edward D. Herlihy and partner Matthew M. Guest wrote in the letter, adding that attacks by short sellers are not related to fundamental performance and put the U.S. economy at great risk.

The law firm did not specify any stocks that had been subject to such attack. Wachtell did not immediately respond to a Reuters request for comments.

Wachtell39;s proposal would revive a ban implemented in 2008. During the financial crisis, short selling was temporarily…