An ageing population and inflation-busting health costs will leave the NHS around £6 billion a year short, despite government promises to protect its funding, a leading think-tank has said.

Chancellor George Osborne said the health service budget would rise by 0.1% a year in real terms over the next four years to meet a Tory pledge to ring-fence the NHS from deep cuts elsewhere.

But King’s Fund chief economist John Appleby told The Independent that would be more than wiped out by the fact that the cost of drugs and medical technology rose faster than other prices.

With the “baby boomer” generation entering old age and adding to demand, the NHS actually faced a 1%-a-year spending cut and growing waiting lists, he warned.

“Waiting times will go up, and NHS management may end up telling ministers ‘we simply cannot do the job, given our resources’,” he told the newspaper.

“The funding gap could rise to as much £6 billion a year over the next five years, just in terms of what the service needs to keep up with existing demands and to maintain existing standards.”

Further pressure would be piled on at the end of a two-year pay freeze for GPs, consultants and others earning more than £21,000, he said.

“The next two years will be relatively manageable for the NHS because of pay restraint. But when that comes off then the pressures will be back on budgets.”