This comes after allegations of sexual harassment made against him by two women.
In an e-mail to its alumni yesterday evening, the university's Office of Alumni Relations said it would discontinue all projects with him and his communications consultancy firm, Strategic Moves.
The NUS statement said this was in the light of the allegations made by stand-up comedian Sharul Channa and doctoral researcher Kiran Kandade against Mr Viswa.
NUS said that "the university does not condone any behaviour or action that is disrespectful and disparaging of individuals, regardless of ethnicity, gender, religion or age". It added that the incident between Mr Viswa and Ms Sharul took place during the online interview series, Inconvenient Questions.