Cambridge - first last year - has slipped to second place in the newly published QS World University Rankings. The top university for 2011-12 was Massachusetts Institute of Technology, which climbed two places from last year, with Harvard coming in at third. 

UK universities continued to perform well, with UCL, Oxford, and Imperial coming in fourth, fifth, and sixth. However, following this year's rise in tution fees, there are concerns that this trend will not last;

The QS rankings rate the world's top 400 universities; each institution is judged on teaching, research, graduate employability, and international outlook. But the government's attempts to make it harder to get a student visa, in the wake of the crackdown at London Metropolitan University means that the UK universities could face a decline in numbers of international students. 

Dr Wendy Platt, director general of the Russell Group, warned the government needs to tread carefully here, to avoid pushing "the best and the brightest students away from the UK and into the arms of our competitors."