In this paper, we prove the nonexistence of global solutions to the quasilinear backward parabolic inequality (Formula presented.) with homogeneous Dirichlet boundary condition and bounded integrable sign-changing initial function, where Ω is a bounded smooth domain in ℝN. The proof is based on the derivation of a priori estimates for the solutions and involves the algebraic analysis of the integral form of the inequality with an optimal choice of test functions. We establish conditions for the nonexistence of solutions based on the weak formulation of the problem with test functions of the form (Formula presented.) where u+ and u