PVM Oil Associates, the largest over-the-counter oil brokerage, revealed yesterday it had lost almost $10m after one of its traders engaged in "unauthorised trading" in Brent futures.

"PVM Oil Futures Ltd can confirm that it was the victim of unauthorised trading on Tuesday June 30," it said in a statement. "As a result . . . substantial volumes of futures contracts were held by PVM. When this was discovered, the positions were closed in an orderly fashion. PVM suffered a loss totalling a little under $10m."