Abstract
The symmetry operators generating the hidden Z₂ symmetry of the asymmetric quantum Rabi model (AQRM) at bias ε ∈ 1/2Z have recently been constructed by V. V. Mangazeev et al. [J. Phys. A: Math. Theor. 54 12LT01 (2021)]. We start with this result to determine symmetry operators for the N-qubit generalisation of the AQRM, also known as the biased Dicke model, at special biases. We also prove for general N that the symmetry operators, which commute with the Hamiltonian of the biased Dicke model, generate a Z₂ symmetry.