R eliance on cheap migrant labour has stifled the UK’s productivity, shadow chancellor Rachel Reeves has said. Countries like Japan or South Korea had adapted to ageing populations by increasing the use of robots and technology to increase productivity, Ms Reeves said. But, in the UK, companies had been “slow” to take up new technology because of the availability of workers from overseas, she added. She told a fringe event at the Labour conference in Liverpool: “What policymakers and business leaders said to me in Japan was, well, necessity is the mother of all invention, because they needed the robots…