For an arbitrary invariant $ρ(G)$ of a graph $G$, the $ρ-$vertex stability number $vs_ρ(G)$ is the minimum number of vertices of $G$ whose removal results in a graph $H\subseteq G$ with $ρ(H)\neq ρ(G)$ or with $E(H)=\varnothing$. In this paper, first we give some general lower and upper bounds for the $ρ$-vertex stability number, and then study the edge chromatic stability number of graphs, $vs_{χ^{\prime}}(G)$, where $χ^{\prime}=χ^{\prime}(G)$ is edge chromatic number (chromatic index) of $G$. We prove some general results for this parameter and determine $vs_{χ^{\prime}}(G)$ for specific classes of graphs.