Investors who poured $1.26 trillion into bond funds in the past six years pulled out record amounts of cash last month, leaving the world's biggest fixed-income managers struggling to stem the flow.

The funds saw $61.7 billion of withdrawals as money market mutual fund assets rose $8.17 billion in the week ended June 25, according to TrimTabs Investment Research and the Money Fund Report. Bank of America Merrill Lynch's Global Broad Market Index dropped 2.9 percent in the past two months, the most since the inception of the daily gauge in 1996, as Federal Reserve Chairman Ben S. Bernanke laid out possibilities for reducing the $85 billion in monthly bond purchases supporting the economy.

Market bears say losses are just getting started because yields barely exceed inflation, leaving little relative value in bonds as the global economy improves. Pacific Investment Management Co., BlackRock Inc., and DoubleLine Capital LP, which together oversee about $6 trillion in assets, said the worst is already over because the securities are fairly valued.