  The most metal-poor tail of the Milky Way ([Fe/H] $\leq$ $-$2.5) contains a
population of stars with very prograde planar orbits, which is puzzling in both
their origin and evolution. A possible scenario is that they are shepherded by
the bar from the inner Galaxy, where many of the old and low-metallicity stars
in the Galaxy are located. To investigate this scenario, we use test-particle
simulations with an axisymmetric background potential plus a central bar model.
The test particles are generated by an extended distribution function (EDF)
model based on the observational constraints of bulge stars. According to the
simulation results, a bar with constant pattern speed cannot help bring stars
from the bulge to the solar vicinity. In contrast, when the model includes a
rapidly decelerating bar, some bulge stars can gain rotation and move outwards
as they are trapped in the co-rotation regions of the bar. The resulting
distribution of shepherded stars heavily depends on the present-day azimuthal
angle between the bar and the Sun. The majority of the low-metallicity bulge
stars driven outwards are distributed in the fourth quadrant of the Galaxy with
respect to the Sun, and about 10$\%$ of them are within 6 kpc from us. Our
experiments indicate that the decelerating bar perturbation can be a
contributing process to explain part of the most metal-poor stars with prograde
planar orbits seen in the Solar neighborhood but is unlikely to be the dominant
one.
