John McDonnell once spoke of how he had to restrain himself from using “physical force” against Nick Clegg, as he described Coalition ministers as “b------s”, it has emerged.

The would-be chancellor told students during a tuition fees protest that he found it “very difficult not to use physical force” on the deputy prime minister in Parliament at the time.

The Labour MP’s remarks about Sir Nick came in an address to students taking part in an occupation of University College London in November 2010 over spending cuts and the Coalition’s raising of the cap on tuition fees. Sir Nick had promised in the 2010 election campaign to abolish fees.

In a video of Mr McDonnell’s remarks, he is recorded as saying: “It is about basic freedom of education. We fought over a generation, people like me, for the right to free education and these b------s are going to take it off us. I think that you’re having the effect. Whatever they say, whatever Clegg says. And it is very difficult not to use physical force on Clegg. I know, I try to restrain myself.”