A search for time-integrated CP violation in D0→h−h+ (h=K, π) decays is presented using 0.62  fb−1 of data collected by LHCb in 2011. The flavor of the charm meson is determined by the charge of the slow pion in the D*+→D0π+ and D*−→¯¯¯D0π− decay chains. The difference in CP asymmetry between D0→K−K+ and D0→π−π+, ΔACP≡ACP(K−K+)−ACP(π−π+), is measured to be [−0.82±0.21(stat)±0.11(syst)]%. This differs from the hypothesis of CP conservation by 3.5 standard deviations.