Party populism is a growth industry in European political science, yet the vast majority of such analysis has focussed on (radical) right-wing populism. European left-populism is still rarely discussed in depth, either in single-case studies or comparatively. But a study of left-populism is relevant for several reasons: first, it will contribute to the vigorous ongoing theoretical and conceptual debate about what populism is as a phenomenon. Second, it will illuminate the discussion of the growing party populism by incorporating a greater number of cases that can be compared with the ‘usual suspects’ on the right. Third, discussion of left-populism is very timely. The post-2007 economic depression is arguably tailor-made for left-populists, both in Europe and wider afield. Accordingly this paper aims to broaden and deepen the emerging literature on left-populism by comparing the nature of populism between two right-wing parties (BNP, UKIP) and two left-wing populist parties (SSP and Respect).