A leading academic is warning that radical Islamic ideology has grown much faster and spread much farther in Britain’s universities than the government wishes to acknowledge: Islamic extremists ‘infiltrate Oxbridge’.

Leading universities including Oxford and Cambridge have been targeted by Islamic extremists who remain widely active on campuses, a prominent academic is warning.

Up to 48 British universities have been infiltrated by fundamentalists and the threat posed by radical groups must be “urgently addressed”, according to Prof Anthony Glees.

The claim calls into question the Government’s attempted crackdown on Islamic extremism in universities and casts doubt on claims by Bill Rammell, the Higher Education Minister, that the problem is not widespread.

Prof Glees will warn the Association of University Chief Security Officers (Aucso) next month that the disbanded extremist group, al-Muhajiroun, claims to have infiltrated “the main campuses such as Cambridge, Oxford, the London School of Economics and Imperial College”.

His speech on “radicalism in universities” also states that at its peak before the July 7 bombings in 2005, al-Muhajiroun had a presence at “more than 48 universities and faculties”, and that Omar Bakri Mohammed, the group’s founder, claims it is “still operational” in several campuses.