Al-Muhajiroun and National Action are proscribed under the Terrorism Act 2000. Membership is illegal and these groups should not be given a platform at universities.
Universities have a legal duty to take reasonable steps to ensure freedom of speech, including for visiting speakers (under the Education Act (No 2) 1986). The government therefore, does not support blanket no-platforming of individuals or organisations who are legally exercising their right to freedom of speech; it is for universities to balance their legal duties on a case-by-case basis.
The government’s position on this issue has been publicly stated on a number of occasions.