More than half the academic staff at London Metropolitan University – around 840 people – are on zero-hours contracts. Their hours of employment vary from term to term or year to year. Most earn nothing during the university holidays. They do the same work as permanent staff but have no job security, minimal prospect of advancement and inferior benefits. Many are teaching courses that they designed: their work is not incidental or unskilled. They can be fired at a month's notice. Many have been in this position for years.

The local branch of the Universities and Colleges Union (UCU) held a protest outside one of London Met's buildings on Holloway Road last Tuesday. Christina Paine, a UCU representative, told the crowd that hourly-paid staff do 'essential work for the university, but they're treated like McDonald's workers'. Rather like a McDonald's manager describing his sixth-form workforce, the university says that many members of staff 'welcome the flexibility hourly-paid contracts provide'. If this were true it would have nothing to lose by offering them full-time, permanent contracts. A spokesman added that there's no reason to single out the Met: 'Lots of universities use zero-hours contracts,' he said. 'I hope you'll write that.'

He's right. According to figures obtained by the UCU from 142 universities last year, more than 24,000 employees are on zero-hours contracts. Almost half the universities that responded employed more than 200 staff on zero-hours. London Met didn't respond to the survey, but the figure of 840 would make it the eighth largest zero-hours employer among UK universities. (Edinburgh, which employed 2712 staff on zero-hours in 2013, has since announced it intends to end the practice.)

The Universities and Colleges Employers' Association (UCEA) prefers not to focus on zero-hours, but instead talks about ‘atypical’ working. Atypical workers include professionals from outside academia who contribute occasional teaching on specialist courses, postgraduate students fitting a small teaching commitment around their studies, or researchers recruited for specific, time-limited projects. When considering such staff, the UCEA argues, the total headcount is misleading – if their contribution is appropriately weighted, they make up only 3.7 per cent of the full-time equivalent of academic staff. According to London Met, casualisation in higher education isn't a problem because everybody does it; according to the UCEA, it isn't a problem because it isn't really happening.

But the 3.7 per cent figure doesn't reflect the importance of casual staff (on various kinds of contract) to teaching. And a calculation based on the number of hours reported by the universities is unlikely to be a true reflection of the work that casual staff do. All hourly-paid teaching positions pay for time spent with students, but whether they pay enough for the extra hours of preparation, administration and marking depends on the university or department. I mark essays for courses at both UCL and King's College London, and can't do it in the time specified in my job description. I either have to do my job inadequately or work unpaid overtime. A survey of teaching assistants and postdoctoral teaching fellows at SOAS earlier this year found that staff were only paid for around half the work they do. Their effective hourly rate was less than the London living wage.

UCU has a national anti-casualisation campaign, but it has received few resources and little attention from the national executive. The centrepiece of a recent UCU 'day of action' on casualisation consisted of getting members to write to their MP. The union has tended to protect the profession by protecting the pay and conditions of its most secure members. But that security is undermined by the reshaping of the profession at the margins – which are moving ever closer to the centre. If the Union wants to win or retain the trust and loyalty of precarious, mostly younger members it needs to listen to them. According to Robert Murthwaite, a law lecturer at London Met, 'change is coming, and it's coming from below.'