The invention provides a polymeric photoinitiator, most suitably a polyurethane photoinitiator, obtained by step-growth co-polymerization of at least one monomer (A) with at least one monomer (B). Monomer (A) comprises a photoinitiator moiety, while monomer (B) is a monomer reactive with monomer (A) to form a polymer. The invention also provides a method for producing said polymeric photoinitiator, a method of cross-linking the polymeric photoinitiator and the use of said polymeric photoinitiator as a photoinitiator of radical polymerization.