A polymer for use in a composition or method of laundry treatment is a copolymer of: (a) one or more anionic monomer units; (b) one or more cationic monomer units; and (c) optionally, one or more uncharged monomer units; wherein, the number ratio of the total of all negative charges on the anionic monomer unit(s) to the total of all positive charges on the cationic monomer unit(s) is from 10 : 1 to 3 : 1, especially from 17 : 3 to 3 : 1.
