Securities customers will gain twice the current federal insurance on cash credit balances and securities held by insolvent broker-dealers under proposed amendments to the 1970 Securities Investor Protection Act which passed the House this week.

The legislation, when is pending in the Senate, would increase the quaranty on cash balances to $40,000, while boosting the securities protection to $100,000.

The amendments, which are expected to come to a Senate vote early next year, also would provide the federal courts and the secruities Investor Protection Corp. with speedier and more flexible procedures for handling such claims. The SIPC works in much the same way as the Federal Deposit Insurance Corp.

In addition, the bill provides that SIPC employees be named trustee for the assets of insolvent brokers dealers and permit the direct payment of customers in some small liquidations.

Franz Opper, a staff member of the House Committee on Interstate and Foreman Commerce and the originial legislation which was created in response to the Wall Street back-office paper crisis in the late 1960's, is terribly cumbersome to work with and expensive and time consuming."

Opper said the amendments, which were first proposed in 1975, would "streamline liquidation procedures and make them less costly."

A major change proposed by the amendment would allow the investor to get the same cash and securities he had when the broker-dealer went under. Under the original act, if an investor had 100 shares of stock and a cash balance with a broker, he might receive only some of the stock and additional cash to make up the difference.

Under the new proposal. Opper said. "He will probably get what he had. Under the old system, there could have been adverse tax consequences if he was given cash instead of the stock. And, he might have wanted the stock." Opper referred to the tax advantage given for capital gains such as stock transactions - over cash holdings.