For a locally compact group
$G$ and
$1\,<\,p\,<\,\infty $, let
${{A}_{p}}\left( G \right)$ be the Herz-Figà-Talamanca algebra and let
$P{{M}_{p}}\left( G \right)$ be its dual Banach space. For a Banach
${{A}_{p}}\left( G \right)$-module
$X$ of
$P{{M}_{p}}\left( G \right)$, we prove that the multiplier space
$\text{M}\left( {{A}_{p}}\left( G \right),{{X}^{*}} \right)$ is the dual Banach space of
${{Q}_{X}}$, where
${{Q}_{X}}$ is the norm closure of the linear span
${{A}_{p}}\left( G \right)X\,\text{of}\,u\,f\,\text{for}\,u\,\in \,{{A}_{p}}\left( G \right)\,\text{and}\,f\,\in \,X$ in the dual of
$\text{M}\left( {{A}_{p}}\left( G \right),{{X}^{*}} \right)$. If
$p\,=\,2$ and
$P{{F}_{p}}\left( G \right)\subseteq X$, then
${{A}_{p}}\left( G \right)X$ is closed in
$X$ if and only if
$G$ is amenable. In particular, we prove that the multiplier algebra
$M{{A}_{p}}\left( G \right)\,\text{of}\,{{A}_{p}}\left( G \right)$ is the dual of
$Q$, where
$Q$ is the completion of
${{L}^{1}}\left( G \right)$ in the
$||\cdot |{{|}_{M}}$-norm.
$Q$ is characterized by the following:
$f\,\in \,Q$ if an only if there are
${{u}_{i}}\,\in \,{{A}_{p}}\left( G \right)$ and
${{f}_{i}}\in P{{F}_{p}}\left( G \right)\left( i=1,2,... \right)$ with
$\sum\nolimits_{i=1}^{\infty }{||}\,{{u}_{i}}\,|{{|}_{{{A}_{p}}\left( G \right)}}||fi|{{|}_{P{{F}_{p}}\left( G \right)}}\,<\,\infty $
such that
$f=\sum{_{i=1}^{\infty }\,{{u}_{i}}{{f}_{i}}}$ on
$M{{A}_{p}}\left( G \right)$. It is also proved that if
${{A}_{p}}\left( G \right)$ is dense in
$M{{A}_{p}}\left( G \right)$ in the associated
${{w}^{*}}$-topology, then the multiplier norm and
$||\cdot |{{|}_{{{A}_{p}}\left( G \right)}}$-norm are equivalent on
${{A}_{p}}\left( G \right))$ if and only if
$G$ is amenable.