The financial sector’s total losses from the credit crisis are approaching $1,000bn after recent turmoil in the markets triggered a further drop in the value of mortgage-backed securities and other debt securities.

Writedowns by Fannie Mae, the US mortgage financier that was nationalised this year and AIG, the insurer that has twice been bailed out by the US government, have lifted total losses reported by financial institutions since the beginning of 2007 to $918bn, according to data compiled by Bloomberg.