New York, NY —

New York State Attorney General Andrew Cuomo struck a deal with the top three credit rating agencies as part of his investigation into the ongoing sub-prime loan crisis.

It's designed to keep investment banks from shopping around for positive ratings for their investment vehicles by requiring the ratings firms to disclose which banks ask them to review potential deals.

David Reiss, an associate professor at Brooklyn Law School, has written about the mortgage loan crisis and says this provision will have the biggest impact.

REISS: To the extent that there's information out there that they are shopping a particular pool of mortgages around, it would imply that they weren't getting the answer that they wanted so it would be information to investors that maybe this pool isn't as good as it was ultimately labeled to be.

REPORTER: Standard and Poor's, Moody's and Fitch have been criticized for underestimating the risk in mortgage-backed securities.

Under the agreement, Cuomo says firms will change their fee structure so they no longer work on commission.