A radiation-sensitive composition includes a free radically polymerizable component, an initiator composition capable of generating free radicals sufficient to initiate polymerization upon exposure to imaging radiation, an infrared radiation absorbing dye having a tetraaryl pentadiene chromophore, a polymeric binder comprising a polymer backbone to which are directly or indirectly linked poly(alkylene glycol) side chains, and a nonionic phosphate acrylate having a molecular weight of at least 250. This composition can be used to prepare a negative-working imageable element that is sensitive to suitable imaging radiation and can be imaged at relatively low energy and developed either on-press or off-press.