London Mayor Ken Livingston has said a planning gain supplement “would not work in London and could actually hinder development.” Speaking at the Town and Country Planning Association conference he added: “Given the failure of previous forms of development taxation the government should instead revise the section 106 process to make it more strategic.” Kate Barker, who devised the supplement, said that consultation into the planning gain supplement should consider why developers favour a tariff system. “The problem with a tariff is that it could be inflexible if we start to get land prices moving around,” she said. She added: “It is possible as we move through time that we will see land prices declining – in which case profit will decline.”