The CP-violating asymmetry View the MathML sourceasls is studied using semileptonic decays of View the MathML sourceBs0 and View the MathML sourceB¯s0 mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample corresponding to an integrated luminosity of 1.0 fb−11.0 fb−1. The reconstructed final states are View the MathML sourceDs±μ∓, with the View the MathML sourceDs± particle decaying in the ϕπ±ϕπ± mode. The View the MathML sourceDs±μ∓ yields are summed over View the MathML sourceB¯s0 and View the MathML sourceBs0 initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain View the MathML sourceasls=(−0.06±0.50±0.36)%, where the first uncertainty is statistical and the second systematic.