Goldman Sachs has defended a secretive trading practice which has come under fire from the Securities and Exchange Commission (SEC).Last week, the SEC voted unanimously to increase the transparency of so-called dark pools, which are anonymous trading platforms where buyers and sellers can keep the details of prices and deals secret from the wider public.Goldman Sachs told the SEC that dark pools were beneficial to investors and traders as they reduced transaction costs and increased competition, bringing more liquidity to global financial markets.But the SEC has proposed that information about investments be made public, as well as requiring those operating dark pools to identify themselves to the public whenever they make a trade.Mary Schapiro, chairman of the SEC, said: "We should never underestimate or take for granted the wide spectrum of benefits that come from transparency, which plays a vital role in promoting public confidence in the honesty and integrity of financial markets."Earlier this month, the SEC's new hard line on financial institutions and their practices saw an investigation by the body lead to the arrest of billionaire hedge fund manager Raj Rajaratnam on insider trading charges.By Gary Cooper