Wall Street firms affected by mortgage losses and writedowns have cut more than 34,000 jobs in the past nine months, the most since the dot-com boom fizzled in 2001, Bloomberg reported.

Citigroup Inc., Lehman Brothers Holdings Inc. and Morgan Stanley are among the firms that have disclosed headcount reductions so far. After the Internet bubble burst, 39,800 jobs were eliminated in a similar time span; the number climbed to 90,000 in the next two years, according to the Securities Industry and Financial Markets Association

The collapse of the subprime mortgage market last year and the resulting credit contraction have weighed down the world’s largest financial institutions with at least $200 billion of writedowns and losses.

Securities firms started eliminating positions in mortgage departments as early as last July, when rising delinquencies on home loans to borrowers with poor credit histories led to a decline in the prices of bonds tied to the loans. Between July and December, almost 17,000 jobs were lost, according to data collected by Bloomberg.

Bloomberg compiled a table showing jobs eliminated by the biggest banks and securities firms since the collapse of the subprime mortgage market in July 2007. The figures are based on company disclosures. Citigroup was at the top with a total of 6,200 jobs cut; Lehman Brothers followed with 4,990. The chart listed a total of 34,463 headcount reductions for the various companies.