The rating agencies Moody's Investors Service and S&P Global downgraded Credit Suisse's ratings after the announcement of a far-reaching restructuring program.
Moody's lowered the long-term rating of the major Swiss bank by one notch from "A2" to "A3".
The agency said the outlook for a number of ratings remained negative.
Moody's justified the rating cuts with the risks involved in implementing the restructuring of the group.
The complexity of the spin-off of the investment bank and the simultaneous handling of other business areas will take a long time and harbor a high risk that important employees and customers could leave the bank.
Added to this is the deteriorating economic environment.
S&P Global downgraded the long-term rating from BBB to BBB-.
Credit Suisse is just about in the investment-worthy area.
Ratings below BBB- are considered junk in the bond market.
The S&P analysts also justified their decision with the risks of restructuring the group in the current difficult economic and market environment.
Nevertheless, according to a media report, Qatar's sovereign wealth fund is considering increasing its stake in the crisis-ridden Credit Suisse.
The Qatar Investment Authority (QIA) wants to participate side by side with the Saudi National Bank in the Swiss bank's share placement, as the "Financial Times" reported on Wednesday, citing insiders.
According to earlier information, Credit Suisse wants to raise a total of CHF 4 billion with a subscription rights offer for existing shareholders and a placement with professional investors.
The Saudi National Bank has already announced that it intends to participate in the share placement.
According to the newspaper report, QIA and two other investors are also involved.
The third investor is a Swiss group, but not a competing bank.
The largest investor, with a 10 percent stake, the US fund house Harris Associates, will not participate in the share placement, but is likely to buy more shares as part of the rights issue, it said.
QIA owns around 5 percent of Credit Suisse.
Olayan Group, an investment company owned by a wealthy Saudi family, is also expected not to participate in the share offering but will retain its approximately 5 percent stake in the bank by participating in the rights issue.
The Financial Times reports that the Saudi National Bank (SNB) will not exceed the threshold of 10 percent with its stake in order to avoid complications with the Swiss supervisory authority.
After the two capital increases, the SNB, QIA and Olayan would together hold 20 to 25 percent of Credit Suisse shares.