There is described a composition for forming an contact lens, in particular for forming a silicone hydrogel contact lens, comprising at least one first vinylic monomer or macromer having one first ethylenically unsaturated group and at least one second vinylic monomer or macromer having one second ethylenically unsaturated group, wherein the first and second ethylenically unsaturated groups are different from each other and wherein the composition further comprises a crosslinker with at least two ethylenically unsaturated (polymerizable) groups with a selected kinetic copolymerization parameter ? of less than 1.0 relative to one of the first and second ethylenically unsaturated (polymerizable) groups as defined above.