Workers at Lambeth College are balloting for strikes to defend their terms and conditions.
The UCU union members are locked in a long-running dispute with college principal Mark Silverman.
He wants to impose new contracts that will slash holidays, increase working hours and cut sick pay. Eventually the contracts would apply to all staff.
Workers last month voted to reject revised proposals from Silverman by an overwhelming 92 percent.
The offers still contained serious attacks.
The new ballot for strikes ends on 17 November.