He has had to counter widespread scepticism that the concept is “too woolly, too vague” and, more damagingly, that it is really just cover for cuts.
Even supporters of the concept question how it can work at a time of deep cuts to local government and Whitehall budgets and support for charities.
This week the Prime Minister enlisted the support of private equity pioneer Sir Ronald Cohen to drive a so-called Big Society Bank. Sir Ronald funded Gordon Brown’s leadership campaign and is understood to have contributed up to £2.5 million to the Labour Party in the past.
The financier has long been associated with the theory of social capital and was an early advocate of using the funds from dormant bank accounts to fund social spending. He hopes to harness at least £400 million from such forgotten accounts and £200 million of permanent capital from the financial services industry.
But even he conceded that the public spending cuts would make achieving the goals a lot harder. He told the BBC: “You cannot possibly make up for tens of billions of pounds of cuts.”
Cabinet Office minister Francis Maude said he regretted that council cuts had meant the inevitable closure of many or most legal aid law centres and Citizens Advice branches but the Big Society was not simply about “formal organisations”.
TUC general secretary Brendan Barber said: “The most worrying thing about the Big Society is that the Prime Minister truly believes that policies of slash, burn and sack will make all our lives better.”
Meanwhile, Mr Cameron sought to engage 16-year-olds when he said he is using Facebook to encourage school-goers to register for one of 12 pilots of his flagship National Citizen Service programme.
