Without the likes of Marie Lewis, further education would collapse.
She is just one of the troopers in a 77,000-strong army of part-time lecturers who teach in FEcolleges around the country.
Despite being a well-qualified sociology and psychology teacher, she is paid by the hour like a piece-worker and employed on an indefinite variable-hours contract.
Ms Lewis is a permanent employee yet has no control over how many hours she will teach each year or how much she will earn. In fact, her hours could even fall to zero but in practice they have ranged from 200 to 900 hours a year.
The 43-year-old mother of two teaches at Huddersfield technical college and is one of 700 part-time lecturers in her college.
According to the Learning and Skills Council, in 2002-3 two-thirds of lecturers were working part-time, compared with one-third a decade ago.
Since colleges became independent corporations in early 1993, money-saving measures have led to many thousands of staff redundancies, and the re-hiring of many lecturers as part-timers, often via employment agencies.
Indeed, many in the sector believe that the casualisation of the college workforce since the 1990s has been a disaster.
Today, almost two-thirds of the part-time teaching force - about 49,000 - are female. There are slightly more women among those on fractional contracts, but an overwhelming majority of those are on short-term hourly paid contracts, and many of these part-timers are older teachers.
The Commission for Black Staff in Further Education found in 2002 that black staff are more likely than white staff to work part-time. The lecturers' union Natfhe estimates that at some 50 per cent of part-time lecturers are paid hourly and are on temporary contracts. But there are no precise figures on the employment status of all 7,000 part-timers.
Research by FE's national training organisation Fento found the proportion of part-timers in colleges varies from a few per cent to almost 90 per cent of the workforce in some cases. It also found that, in 67 per cent of cases, part-timers made a positive choice to work in this way.
Other evidence suggests the proportion of part-timers is particularly high in basic skills, hairdressing and language teaching.
The former Further Education Funding Council, which was abolished in 2001, found that part-timers were often less well-qualified than other staff. It also found that only 25 per cent of part-timers offered extra-curricular support to students or took part in staff development activities.
While any college lecturer is eligible for the national teacher's pension scheme, self-employed lecturers hired through agencies and third-party providers are not.
Dr Joanna Martin, managing director of the employment agency Protocol Professional, says that 70 per cent of teaching should be done by permanent staff.
"Many colleges recognise that by recruiting people through us they save a lot of money in overhead costs," she says.
"They just don't have the structure to deal with people on a casual or hourly rate.
"Plenty of colleges take 200 or 300 people through us. These numbers are often very high because many people are teaching a very small number of hours. The administrative implications of dealing with two hours here and three hours there are huge."
But in the past few years there have been some positive signs that the trend towards casualisation has begun to be reversed. Colleges have been using the Government's Teachers' Pay Initiative to move staff from hourly rates to contracts.
The 1998 Education and Employment Select Committee report on FE concluded:
"It is the nature of the employment contract between staff and employer that is the overriding concern, not the distinction between full-time or part-time, agency employer or college employer."
Natfhe argues that in each case minimum standards of employment practice must be met, and that teaching staff must be fully involved in and committed to the work of the college. All staff, says the union, should have access to appropriate training and development opportunities.
A national agreement signed in 2000 between unions and the Association of Colleges was intended to ensure that part-time employees are not treated less favourably than their full-time colleagues on a range of contractual terms and benefits, including pay, holidays and professional development.
It also states that "both sides recognise fulfilment of the requirements of this agreement, and the Part-Time Workers Regulations 2000 can best be achieved by using fractional contracts of employment for part-time employees."
But the agreement also concedes that a range of contracts, including variable hours and fixed-term, may still be used. In practice many colleges still employ part-timers casually because it is cheaper.
Barry Lovejoy, Natfhe's head of colleges, says: "The problem is where people are constantly re-engaged on fixed-term contracts and very often hourly-paid because that really is a form of casualisation.
"The most extreme form is where there is an overuse of agencies so that there is no employment relationship between college and individual, and the lecturer is supposedly self- employed.
"In itself, being part-time is not the problem. It is the nature of the contract that we are particularly concerned about.
"We are all in favour of part-time employment with proper conditions. That is still the major issue that needs to be addressed - the heavy reliance on fixed-term, hourly paid lecturers.
"We are not against part-time work or flexibility, but what we want is contracts that give people some sense of security."
Paul Mackney, general secretary of Natfhe, says colleges should not employ people as part-timers if they are working the same hours as permanent staff, because, he says, "We have no problem with a good agency that supplies temporary staff. However, we do have a problem with one that supplies temporary staff as if they were permanent staff - because in the end that denies people their rights."