Nearly two out of every three colleges have teachers on controversial zero-hour contracts, research from the University and College Union (UCU) has suggested.
It asked 275 colleges about the contracts and said that around 61 per cent of the 200 who answered employed teaching staff on contracts that offered no guarantee of work.
The government is currently investigating use of the contracts amid criticism they create uncertainty in the workforce, leaving staff without sick or holiday pay, and for making it difficult to get tenancy agreements, credit cards or loans because it is impossible to show a regular income.
But proponents of the contracts argue they allow for flexible working patterns and mean employers can take on more staff.
However, Simon Renton, UCU president, said: “Our findings shine a light on the murky world of casualisation in FE.
“The extent of the use of zero-hour contracts is difficult to pin down, as various groups have found, but their prevalence in our colleges leads to all sorts of uncertainty for staff.
“Without a guaranteed income, workers on zero-hour contracts are unable to make financial or employment plans on a year-to-year, or even month-to-month basis.
“Employers cannot hide behind the excuse of flexibility — this flexibility is not a two-way street and, for far too many people, it is simply a case of exploitation.
“Their [zero-hour contracts’] widespread use is the unacceptable underbelly of our colleges.”
The contracts have already come under fire from Deputy Prime Minister Nick Clegg.
He said in July: “Families have to plan to pay bills – everyone has to plan for what their income is and what they are going to pay out. That can cause very intense insecurity and anxiety indeed.”
The Association of Colleges (AoC), which drew up legal advice to help colleges respond to UCU questioning on zero-hour contracts, defended the agreements saying they benefited colleges and staff.
Emma Mason, association director of employment policy and services, said: “We know zero-hour contracts suit some staff, for example professionals who wish to teach for a small number of flexible days every term but do not want to be full-time teachers or exam invigilators whose work is of a seasonal nature.
“Colleges do not restrict people on zero-hour contracts from working elsewhere. In fact, colleges benefit from engaging industry professionals who can ensure training reflects current occupational standards.”
Nevertheless, the UCU’s research – which used the Freedom of Information Act to approach FE colleges in England, Wales and Northern Ireland – comes ahead of the results of an investigation into zero-hour contracts by the Department for Business, Innovation and Skills (BIS).
“We are encouraged that both the government and the opposition have said they will be looking at zero-hour contracts, but neither side has yet said anything that will give the thousands of people subjected to these conditions much hope,” said Mr Renton.
However, the UCU’s research came in for criticism from the association, a month after it sought positive examples of colleges’ zero-hour contracts following talks with BIS about its investigation.
“The UCU data does not cover all FE staff — it analyses the proportion of teaching staff employed on zero-hour contracts across the colleges that responded to the FOI request,” said Ms Mason.
“The figures do not cover all colleges and include estimations of headcount, so do not represent a true picture.”
She added: “While the UCU data gives an indication of the use of zero-hour contracts for teaching staff, it does not provide evidence of poor employment practice.”
The UCU is due to lead a debate on the zero-hour contracts at the TUC Congress in Bournemouth on Sunday.