In this paper we construct a minimal faithful representation of the $(2m+2)$-dimensional complex general Diamond Lie algebra, $mathfrak{D}_m(mathbb{C})$, which is isomorphic to a subalgebra of the special linear Lie algebra $mathfrak{sl}(m+2,mathbb{C})$. We also construct a faithful representation of the general Diamond Lie algebra $mathfrak{D}_m$ which is isomorphic to a subalgebra of the special symplectic Lie algebra $mathfrak{sp}(2m+2,mathbb{R})$. Furthermore, we describe Leibniz algebras with corresponding $(2m+2)$-dimensional general Diamond Lie algebra $mathfrak{D}_m$ and ideal generated by the squares of elements giving rise to a faithful representation of $mathfrak{D}_m$.