NHS England boss Simon Stevens has been accused of giving "woolly" answers to MPs about how the health service will achieve £22 billion of efficiency savings.
Mr Stevens was giving evidence to the House of Commons Health Committee on a range of topics affecting the NHS, telling the panel that the "single most important thing we've got to do" is turn around spending on agency staffing, which cost £3.3 billion last year.
But after being asked for details on improving the NHS's finances, Labour MP Emily Thornberry told him: "I haven't really met a health professional that entirely believes that we can have £22 billion of efficiency savings, and some of them have been cheeky enough to say they really don't think that you believe it either.
"It would reassure us I suppose if you were able to come to this committee and perhaps be a little bit more specific. To not be able to come to us without even a ball park kind of breakdown of where the figures are - it's kind of a bit, if you don't mind me saying, a bit woolly."
Referring to NHS England's five-year plan which was published in October, Ms Thornberry added: "To come to us nearly a near later and not be able to give us any more specific details about this is very disappointing."
Asked about proposed £200 million cuts to local authorities' public health budgets, Mr Stevens told MPs: "I don't think we want more of that kind of approach going forward."
He said a "more assertive posture" was needed on tobacco, alcohol, junk food and sugary drinks.