A high-strength multiphase steel with minimum tensile strengths of 580 MPa, preferably having a dual-phase structure for a cold-rolled or hot-rolled steel strip with improved forming properties, particularly for lightweight vehicle construction contains the elements (contents in mass-%): C 0.075 to ≦0.105; Si 0.600 to ≦0.800; Mn 1.000 to ≦2.250; Cr 0.280 to ≦0.480; Al 0.010 to ≦0.060; P≦0.020; N≦0.0100; S≦0.0150, remainder iron, including typical steel-accompanying elements not mentioned above, which are impurities introduced by smelting, with the condition that the Mn content is preferably ≦1.500% for strip thicknesses up to 1 mm, the Mn content is preferably ≦1.750% for strip thicknesses of 1 to 2 mm, and the Mn content is preferably ≧1.500% for strip thicknesses ≧2 mm