DETROIT — General Motors Corp., which is planning big job cuts and plant closings as it fights to avoid bankruptcy, said Thursday it lost $4.8 billion in the fourth quarter and $8.6 billion in all of 2005, dragged down by losses and charges in its North American division.

It was the fifth-straight quarterly loss for the world's largest automaker and the worst annual loss since 1992. GM's North American operations alone posted adjusted losses of $1.5 billion for the quarter and $5.6 billion for the full year, as unit sales fell 3 percent in North America in 2005.

The dismal results were far worse than Wall Street expected. GM's stock price, which had already fallen about 36 percent since July, slumped another 80 cents, or 3.4 percent, to close at $23.05 on the New York Stock Exchange.

GM Chairman and CEO Rick Wagoner said 2005 "was one of the most difficult years in GM's history."

"Two significant fundamental weaknesses in our North American operations were fully exposed — our huge legacy cost burden and our inability to adjust structural costs in line with falling revenue," Wagoner said in a statement.