Plans to turn the NHS into a “world class” commissioner of health care are highly unlikely to work, a former health department head of strategy has warned.

But if the government does succeed, its achievement will be “a world first,” said Chris Ham, professor of health services management at Birmingham University and former head of the Department of Health’s strategy unit.

Separating the role of purchasing from the provision of health care has now been tried in various ways in several European countries, in New Zealand, and in the United States, …