Clinical commissioning groups will have some control over new pooled health and social care budgets but the extent has yet to be decided, according to Sir Malcolm Grant.

The NHS England chair said locating funds to contribute to the pooled budget would be “very difficult” for the NHS. He said it was not yet clear how the money would be freed up in the NHS or “where it is going to”.

He said: “It won’t take effect until 2015-16 but we need to get absolute clarity on [this] in order to manage the period up until then, so it becomes as smooth a transition as possible.” His comments follow confusion about whether the fund would be held by CCGs or local authorities, and where the money would come from.

Sir Malcolm said: “The critical thing is to ensure the money goes through CCGs, and my understanding is that has been agreed.”

He said this meant CCGs would have “a certain amount of control, extent yet to be specified” over the money.

Asked whether there should be greater merging of health and social care budgets in future, he said he was “doubtful” that would achieve integrated services.

He said: “This [pooled budget] is a big step, and a big experiment. They are two different budgeting systems and cultures, and for some, social care is a paid for service, the NHS is free at the point of delivery.

“So big changes in philosophy are in the balance here.

“I’m quite pragmatic about this. It [budget integration] may need to go further but I don’t think there’s a magic bullet.

“We’ve got to get away from this notion that a single legislative change can bring about transformation. We need to experiment.”