The latest data from Goldman Sachs Group's prime brokerage unit shows that hedge funds upped their short bets in eight out of the 10 previous sessions up to last Monday having rushed to unwind bullish stock bets as the recent stock market rally slowed, according to a report by Bloomberg.

The report cites Goldman's Vincent Lin as revealing that, at the August midpoint, the dollar amount of bearish wagers was more than double the volume of positions covered in the whole of July.

An uptick in short sales last week was also reported by Morgan Stanley’s securities lending desk, particularly among single stocks, with Wednesday and Thursday posting the second- and fourth-busiest session of the year, respectively.