Merrill Lynch , Lehman Brothers, Morgan Stanley and Citigroup are among a group of investment banks developing an electronic trading platform for unregistered securities to compete with existing systems such as the one created by Goldman Sachs.

The move comes after Goldman signed up Oaktree Capital, the hedge fund group, and Apollo Management, the private equity firm, to sell unregistered shares through its GSTrUE private trading system. Apollo shares will also trade on a platform created by JPMorgan Chase.