Two years ago in Shanghai, an infant girl with a heart defect was abandoned in the shadow of the luxurious Four Seasons hotel, possibly because her migrant worker parents could not afford her medical care.

That child’s plight cast a sharp light on one of the biggest social problems facing China’s new political leaders: how to improve healthcare for tens of millions of migrant workers who live in desperate poverty amid the conspicuous consumption of its biggest cities.

The abandoned infant, who now lives in an orphanage after her heart repair was paid for by the local government, is one of 230m migrants who have boosted urbanisation to the point where last year, for the first time, more Chinese lived in cities than in the countryside. In Shanghai alone, she is one of nearly 10m migrants who make up 40 per cent of the population – and whose numbers are forecast to rise to 14m, or half the city’s population, by the end of the decade.