Stockbrokers who over leveraged their clients into the recent volatile equities market caused downward pressure on up to 15 stocks.

Investors, under the guidance of some brokers, were effectively creating a carry trade through their margin lending facility, Goldman Sach JBWere head of equities Dion Hersham said.

"For example you borrow your margin loan at seven per cent and then invest it in a 10 per cent yielding infrastructure," Hersham said.

"You gear it up and get the tax benefits and you should be left with a surplus.

"That all works extraordinarily well providing the capital is flat to increasing, but when it is falling, investors are forced to put more money into these vehicles or sell their stakes, and we have seen pronounced examples of that recently.

"I wouldn't say it is a dominant influence on the market but we could certainly point to 10 to 15 stocks that have been absolutely pounded on the back of that strategy," he said.

Last month stockbroker Tricom failed to settle $84 million worth of trades related to margin loans on time.

Tricom margin loan clients had to sell holdings in two listed Babcock & Brown investment vehicles after both share prices were driven lower on January 29.

The flood of margin calls on the portfolios of Tricom clients owning these and other stocks last week triggered a steep rise in trading volumes.

Between 2003 and 2007, the value of margin loans on the Australian market nearly quadrupled from $10 billion to $36 billion.