Reforming tariffs so that the highest users pay the greatest unit charges would hinder the uptake of time-of-use deals, Octopus has warned. The supplier has urged the MPs to back away from their previous support for replacing standing charges with so-called block tariffs. This type of deal, which has been rolled out in Dubai, creates a sliding scale for electricity prices with those in the top usage block paying the most per unit and then progressively reducing.