Two Yorkshire colleges are to axe almost 70 employees, while some of their colleagues will see their salaries cut by as much as #163;10,000.
The University and College Union (UCU) claims Barnsley College's move to slash its budget by a quarter, making up to 30 lecturers redundant, is "disproportionate" to national funding cuts.
Leeds College of Building (LCB) is also looking to cut its staff numbers by 39 jobs, and has offered some employees alternative roles on a much lower salary.
Dave Gibson, UCU branch secretary at Barnsley College, said that around 38 lecturers had already accepted voluntary redundancy, meaning that its workforce was to be cut by up to 25 per cent.
Staff have been told they will have to work longer hours and teach larger classes.
Around 200 members took to the picket line on Friday, and four further one-day strikes are planned before the end of term.
"This is going to have appalling consequences for students' education," said Mr Gibson. "There is an absolute determination to pursue this as strongly as we can. Members think this is an absolute outrage and we are determined to fight on."
But principal Colin Booth said that, following positive talks with union officials, the "worst-case scenario" would see 15 staff made redundant.
"We are disappointed to lose valued staff, but it is simply not possible to balance the college budget for next year without making savings in some departments. There is not a choice - we can't spend money that we don't have.
"Staff reductions will mean an increase in class sizes, with the college's current average class size of 14 increasing to 17. The situation is not ideal, but I am certain that we can deal with the national public funding cuts without an impact on the quality of education."
At LCB, 77 per cent of members who voted in a ballot on industrial action supported going on strike.
The union claims that lecturers at the college - which holds more than #163;10 million in reserves - who survive the cull have been told they will have to work 20 per cent longer hours.
UCU accused the college of reneging on an agreement to protect staff pay for three years.
Regional official Julie Kelley said: "The college has broken its word to staff and seems intent on trying to deliver teaching on the cheap.
"LCB is clearly using the current funding challenges as an excuse to rush through cuts, even though it is in a healthy financial position."
College principal Ian Billyard confirmed that 39 posts were at risk.
"We have entered into full consultation with those that are affected and offered alternative options to staff to try and mitigate the number of compulsory redundancies.
"This has resulted at this stage in a number of enquiries from staff with approximately 20 members of staff taking up one of these options, thereby reducing the number of compulsory redundancies."