Credit Suisse was reportedly earlier this week facing a takeover bid from US financial group State Street.
But the US group has denied plans to acquire the Swiss bank while Credit Suisse branded the rumours 'really stupid'.
A spokesperson for State Street said the bank "is not pursuing an acquisition of, or any other business combination with, Credit Suisse."
"There is no basis to the continuing market rumors," State Street's spokesperson continued. "Although we have a long-standing company policy of not commenting on such speculation, we feel a response to these reports is now warranted in this instance, as we are in the midst of a pending acquisition of Brown Brothers Harriman Investor Services."
While Credit Suisse chief executive Thomas Gottstein yesterday called queries over a potential takeover offer "really stupid", shutting down questions after a report by Swiss newsblog Inside Paradeplatz.
Speaking at the Goldman Sachs European Financials Conference in Rome, Gottstein said "We never comment on rumours. My father once gave me a piece of advice: for really stupid questions, you'd rather not comment at all. I will listen to my father's advice in this instance."
The potential bid was first reported on 8 June by Inside Paradeplatz, which cited an "insider in Zurich" claiming State Street was planning an "imminent" and "friendly" takeover of Credit Suisse.
The bid reportedly valued Credit Suisse at CHF 9 (£7.35) per share, 34% above the bank's current share price of CHF 6.72 (£5.48).
This would value Credit Suisse at CHF 23bn (£18.8bn), which is close to State Street's current valuation of $25.3bn (£20.2bn).
The reports from Inside Paradeplatz noted that Credit Suisse "would probably become a subsidiary of State Street, with a focus on Swiss universal banking and global private banking". It added that the takeover could see the bank's upper management replaced with executives from State Street.
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Credit Suisse had previously declined to comment, instead pointing to an interview with its CEO Thomas Gottstein last month where he said: "We have a total focus on our strategy. We are at a valuation now where we have a lot of upside. If we deliver on our strategy, then our share price will follow and that is what we are focused on."
State Street had earlier added: "We are not going to respond to an earlier news report. As we have previously discussed, we are focused on our pending acquisition of Brown Brothers Harriman's investors services business."
The report came as Credit Suisse said on 8 June that it expected to lose money in this quarter, due to factors such as Russia's invasion of Ukraine, rising interest rates and customer flows.
