Mortgage and subprime lenders have announced nearly 70,000 layoffs in the first three quarters of 2007, according to Challenger, Gray & Christmas Inc., which tracks corporate job cut announcements.

That’s a more than five-fold increase from the 12,874 announced job losses in mortgage lending tallied by Challenger in all of 2006.

“The heaviest job cutting has occurred over the last two months as the bottom suddenly fell out from the mortgage and subprime markets,” said John Challenger, the company’s chief executive officer, in a statement accompanying today’s release of the latest numbers.