The Union of Jewish Students has said it is "unacceptable" that two students linked to extreme Islamist organisation Hizb ut-Tahrir have been elected to lead a student union.
Tarik Mahri and Jamal Achchi were elected by the University of Westminster Students' Union despite the NUS's no-platform policy for the radical group. UWSU does not implement the NUS ban on Hizb ut-Tahrir.
The pair promoted themselves, along with a third candidate, as the "three brothers" and appealed to fellow students to back them to tackle student debt and finance issues.
Mr Mahri, who becomes union president this summer, describes himself as an "outspoken" political activist and has used Twitter and Facebook to post messages supportive of Hizb ut-Tahrir.
Speaking to a student news station before the election, he insisted: "My beliefs are separate from what I'm going to do in the job. This has no relevance to what I'm here to stand for the students with regards to representation."
Mr Achchi shared posts promoting Hizb ut-Tahrir ideologies on the social publishing site scribd.com. They included one document explaining methods that could be used to establish an Islamic caliphate.
Carly McKenzie, UJS campaigns director, said: "This is a truly unacceptable and deeply concerning move by UWSU. Hizb ut-Tahrir ideology directly contravenes the values held by students and their union.
"How these candidates can properly represent all students is beyond me. What's the use of the NUS no-platform policy?"
Last month UJS complained to UWSU about the candidates. The election was postponed, and then re-started with the same candidates.
Mr Mahri and Mr Achchi were successful, while the third of the "three brothers", Adeel Anwar, narrowly missed out on the role of vice-president for communications. Mr Mahri also supports the creation of an Islamic caliphate. Mr Achchi, now vice-president for education, is a fourth-year Arabic and international studies student.
Last year an event with a Hizb ut-Tahrir representative, due to take place on Westminster's campus, was cancelled following pressure from NUS.
NUS president Aaron Porter has told outgoing UWSU president Robin Law of his concern over the election result.
Mr Porter said: "Our rules state individuals or members of organisations or groups identified as holding racist or fascist views are not allowed to stand for election or go to, speak at or take part in conferences, meetings or any other events."