TheStreet.com's Jim Cramer says the acquired Bear Stearns portfolio is worth even less than he thought.

How bad was that Bear Stearns portfolio? I am beginning to believe that JPMorgan's (NYSE: JPM) (Cramer's Take) buy of Bear is looking like a big mistake. It can only be justified by what might have been an even bigger problem for JPM -- the collapse of the trades that Bear made, which were being processed by JPM's clearing.

We are now beginning to get a real sense of the worthlessness of the mortgage portfolios. Not that we got any help from the SEC, which has taken a "we don't care what's in the mortgages as long as you tell us you have mortgages" attitude. That's been worthless for investors, and maybe even for JPMorgan.

The losses now exceed $400 billion, according to my modeling (if you simply assumed that 50% of the exotic mortgages that were issued from 2005 to 2007 eventually went into default). That's amazing, but it looks like I dramatically underestimated the losses. UNDERESTIMATED!

The most egregious issuers of these exotic mortgages were Bear, Merrill Lynch (NYSE: MER) (Cramer's Take) and Lehman Brothers (NYSE: LEH) (Cramer's Take). I believe that JPM has taken in a huge number of uninsurable, non-hedgeable mortgage instruments that are a pure write-off. And that means they are probably underwater on everything they took in.