Let K be an arbitrary field of characteristic not equal to 2. Let m, n\in\mathbb N and V be an m dimensional orthogonal space over K . There is a right action of the Brauer algebra {\mathfrak B}_n(m) on the n -tensor space V^{\otimes n} which centralizes the left action of the orthogonal group O(V) . Recently G.I. Lehrer and R.B. Zhang defined certain quasi-idempotents E_i in {\mathfrak B}_n(m) (see (1.1)) and proved that the annihilator of V^{\otimes n} in {\mathfrak B}_n(m) is always equal to the two-sided ideal generated by E_{[(m+1)/2]} if \mathrm{char} K=0 or \mathrm{char} K>2(m+1) . In this paper we extend this theorem to arbitrary field K with \mathrm{char} K\neq 2 as conjectured by Lehrer and Zhang. As a byproduct, we discover a combinatorial identity which relates to the dimensions of Specht modules over the symmetric groups of different sizes and a new integral basis for the annihilator of V^{\otimes m+1} in {\mathfrak B}_{m+1}(m) .