Although there is consensus that metal-rich stars in the Milky Way bulge are formed via secular evolution of the thin disc , the origin of their metal-poor counterparts is still under debate . Two different origins have been invoked for metal-poor stars : they might be classical bulge stars or stars formed via internal evolution of a massive thick disc . We use N-body simulations to calculate the kinematic signature given by the difference in the mean Galactocentric radial velocity ( \Delta V _ { GC } ) between metal-rich stars ( [ Fe/H ] \geq 0 ) and moderately metal-poor stars ( -1.0 \leq [ Fe/H ] < 0 ) in two models , one containing a thin disc and a small classical bulge ( B/D=0.1 ) , and the other containing a thin disc and a massive centrally concentrated thick disc . We reasonably assume that thin-disk stars in each model may be considered as a proxy of metal-rich stars . Similarly , bulge stars and thick-disc stars may be considered as a proxy of metal-poor stars . We calculate \Delta V _ { GC } at different latitudes ( b = 0 ^ { \circ } , -2 ^ { \circ } , -4 ^ { \circ } , -6 ^ { \circ } , -8 ^ { \circ } and -10 ^ { \circ } ) and longitudes ( l = 0 ^ { \circ } , \pm 5 ^ { \circ } , \pm 10 ^ { \circ } and \pm 15 ^ { \circ } ) and show that the \Delta V _ { GC } trends predicted by the two models are different . We compare the predicted results with ARGOS data and APOGEE DR13 data and show that moderately metal-poor stars are well reproduced with the co-spatial stellar discs model , which has a massive thick disc . Our results give more evidence against the scenario that most of the metal-poor stars are classical bulge stars . If classical bulge stars exists , most of them probably have metallicities [ Fe/H ] < -1 dex , and their contribution to the mass of the bulge should be a small percentage of the total bulge mass .