This article explores the critical role of labour market imperfections in climate stabilisation costs formation. It shows that the degree of rigidity of the labour markets is a central parameter and we conduct a systematic sensitivity analysis of the model results to this parameter. When labour markets are represented as highly flexible, the model results are in the usual range of existing literature, i.e. less than 2% GDP losses in 2030 for a stabilisation target at 450ppm CO2 equivalent. But when labour markets rigidities are accounted for, mitigation costs increase dramatically. In a second time, the article identifies accompanying measures, namely labour subsidies, which guarantees against the risk of large stabilisation costs in the case of high rigidities of the labour markets. That vision complements the usual view that mitigation is a long-term matter that depends on technology, innovation, investment and behavioural change.