"As a consequence, [we] are being criticized by a world that expects more from us," Narasimhan said in the internal email, which was obtained by CNBC.

Narasimhan said "we made a mistake" in entering a contract in February 2017 with Cohen through his company, Essential Consultants, for guidance "as to how the Trump administration might approach certain US healthcare policy matters."

Novartis CEO Vasant Narasimhan told employees in an internal memo Thursday that "yesterday was not a good day" for the company, after the pharmaceutical giant revealed that it paid $1.2 million to President Donald Trump 's personal lawyer, Michael Cohen .

In a statement Wednesday, Novartis said that the one-year agreement, for which Essential Consultants was paid $100,000 per month, "predated Vas Narasimhan becoming Novartis CEO and he was in no way involved with this agreement."

Novartis also said in the statement that it had been contacted by special counsel Robert Mueller's office in November 2017 regarding the agreement.

Payments from Novartis to Cohen's company were first alleged in an explosive report from lawyer Michael Avenatti, whose client, porn star Stormy Daniels, is suing Trump and Cohen to void a nondisclosure deal that bars her from discussing an alleged affair.

Avenatti's report claimed Novartis had paid Essential Consultants nearly $400,000; in the Wednesday statement, Novartis revealed that it had paid $1.2 million to Cohen's company.

Read Narasimhan's full email below: