The advice of a high-powered board of business people set up to counsel the government on working with the private sector was systematically ignored by ministers and civil servants, according to a letter seen by the Financial Times.

The commercial advisory board – whose members included investment bankers, lawyers and a former regulator – quit in September, declaring it was “wasting its time” as the government moved to scrap much of the second wave of independent sector treatment centres (ISTCs) on which it was, in part, advising.