Andy Burnham’s plans to reform social care could cost far more than he is claiming and take “many decades” to be implemented, a leading expert has claimed.

Andrew Dilnot told the Today programme this morning that he was “puzzled” by some of what Burnham said yesterday, and he implied that he was unconvinced by what Burnham was offering.

Dilnot, a former chair of the UK Statistics Authority, is one of the nation’s leading economists and chaired a commission on social care reform for David Cameron’s government in 2010. Although ministers were initially positive about his plan to cap the amount individuals can be required to pay for their social care, successive governments were worried about the cost and the plan was never implemented.

In his interview, Dilnot said that he did not understand why Burnham told the BBC yesterday that his plan would cost less than £18bn a year when what he seemed to be describing – an NHS-style care service, with care free at the point of delivery – would cost a lot more.

Dilnot said he was “puzzled” by Burnham’s answer to the £18bn question because “if we were to make social care free in the same way that health care is largely free, then I think we will be talking about an amount of money well in excess of £18bn.”

Dilnot said that making the English social care system similar to Scotland’s – where personal care is free, but where people who need to go into a care home can still face huge costs for the accommodation element of their care – might cost roughly half of the £18bn mentioned. But that was not what Burnham seemed to be proposing, Dilnot said. He explained:

[Burnham] did talk about making social care free, and what he implied was that he wanted social care to be completely free.

And that’s not at all the case in Scotland, where although the policy is called free personal care, we still have exactly the problem that Mr Burnham himself has talked about of people needing residential care faced with very substantial bills.

And so I think what he’s really talking about probably is social care that looks very like the NHS, that will be entirely free.

What he hasn’t described is how he would raise the funds that he would need for that, and that would be a very substantial sum of money.

Dilnot said that, when Burnham gave a big speech on social care just after becoming PM, he left the impression there could be legislation before the next election.

After yesterday, Dilnot said, reform seems further away. He explained:

It sounds as though there’ll be some more details [of the plans] in the prime minister’s speech tomorrow at his party conference, but I think even that will continue to remain vague.

I think what we learned yesterday was that, if anything, change is now further away than had been implied or suggested.

Dilnot also said the full reform proposed by Burnham could take decades.

I also think that there was an indication in what [Burnham] said that he’s imagining something that could take many years, even many decades before it came to fruition.

So they are now, I suspect, looking at ways of beginning a move in this direction without imagining they can get there very quickly.