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We present a detailed study of emission-line systems in the GAMA G23 region,making use of $\textit{WISE}$ photometry that includes carefully measuredresolved sources. After applying several cuts to the initial catalogue of$\sim$41,000 galaxies, we extract a sample of 9,809 galaxies. We then comparethe spectral diagnostic (BPT) classification of 1154 emission-line galaxies(38$\%$ resolved in W1) to their location in the $\textit{WISE}$ colour-colourdiagram, leading to the creation of a new zone for mid-infrared "warm" galaxieslocated 2$\sigma$ above the star-forming sequence, below the standard$\textit{WISE}$ AGN region. We find that the BPT and $\textit{WISE}$ diagramsagree on the classification for 85$\%$ and 8$\%$ of the galaxies as non-AGN(star forming = SF) and AGN, respectively, and disagree on $\sim$7$\%$ of theentire classified sample. 39$\%$ of the AGN (all types) are broad-line systemsfor which the [\ion{N}{ii}] and [H$\alpha$] fluxes can barely be disentangled,giving in most cases spurious [\ion{N}{ii}]/[H$\alpha$] flux ratios. However,several optical AGN appear to be completely consistent with SF in$\textit{WISE}$. We argue that these could be low power AGN, or systems whosehosts dominate the IR emission. Alternatively, given the sometimes high[\ion{O}{iii}] luminosity in these galaxies, the emission lines may begenerated by shocks coming from super-winds associated with SF rather than theAGN activity. Based on our findings, we have created a new diagnostic: [W1-W2]vs [\ion{N}{ii}]/[H$\alpha$], which has the virtue of separating SF from AGNand high-excitation sources. It classifies 3$\sim$5 times more galaxies thanthe classic BPT

Galaxy and Mass Assembly (GAMA): A $\textit{WISE}$ study of the activity of emission-line systems in G23