Labour was treated to a 45-minute lecture on the moral limits of markets by Harvard University professor Michael Sandel in one of the more extraordinary and cerebral addresses to a Labour conference by a visiting foreign speaker.

The author of Justice, who was asked by party leader Ed Miliband to speak to the conference, said: “If someone is willing to pay for sex or buy a kidney from a consenting adult, the only question standard economics asks is ‘how much?’ Each party decides for himself or herself on what value on the things being exchanged. This non-judgmental stance towards values lies at the heart of market reasoning and explains much of its appeal.”

But he said that a reluctance to engage in moral argument, together with the embracing of markets, had exacted a heavy price: “It has drained our public discourse of moral and civic energy, and it has contributed to the managerial, technocratic politics that has afflicted many societies. A debate about the moral limits of markets would enable us to decide about where markets do and not belong. It would invigorate our politics by welcoming competing notions of the good life into the public square.”