We present here the results of a powder neutron diffraction study on the (1-x) BiFeO_{3 - x}PbTiO₃ (BF-xPT) system, which reveal an abrupt change in magnetic structure from a noncollinear antiferromagnetic one to a collinear G -type antiferromagnetic as the nuclear structure of the ferroelectric phase changes from monoclinic in Cc space group for x £ 0.27 to tetragonal in P4mm space group for  x ³ 0.31 across the morphotropic phase boundary (MPB). This reflects the multiferroic character of the MPB in the BF-xPT system.