Public perceptions of a UK carbon labelling trial were assessed via three focus groups. The public found it very difficult to make sense of labelled emissions values without additional information. There was also little evidence of a willingness to use labels for product selection. There is a strong case for using carbon reduction labels to indicate a programme of on-going emissions reductions, rather than expecting consumers to incentivise emissions reductions by actively choosing the lower carbon variant of two or more products. The normalisation issues and emissions reduction potential of carbon labelling are discussed.