We present results for controlled optical collisions of cold, metastable Ne atoms in a magneto-optical trap. The modification of the ionizing collision rate is demonstrated using a control laser tuned close to the (3s)3P2 to (3p)3D3 cooling transition. The measured ionization spectrum does not contain resonances due to the formation of photoassociated molecules connected to the omega = 5 excited state potential as predicted by Doery et al (1998 Phys. Rev. A 57 3603-20). Instead, we observe a broad unresolvable ionization spectrum that is well described by established theory (Gallagher and Pritchard 1989 Phys. Rev. Lett. 63 957). In order to induce collisions between pairs of trapped metastables, a control laser is tuned to the red of the transition where we measure a factor of 4 increase in the rate for ionizing collisions. We also investigate the effect of optical shielding by tuning the laser to the blue of the transition and observe a factor of 5 suppression in the ionization rate.