Shadow health secretary Andrew Lansley has described the free personal care bill as being under-costed and underfunded as it received its second reading in the House of Commons last night.
The government says the offer of free personal care will cover 110,000 people, who are currently funding either all or part of their own care, and benefit a further 130,000 people from extra investment in reablement.
However, Lansley warned that evidence from Scotland suggested that large numbers of people – more than anticipated – would become claimants of free personal care if it was offered to them.
Lansley said: "We cannot have any confidence about what the cost of this bill will be. By its own admission, the government has nothing other than a gross estimate – a generalised estimate – of how many people are receiving informal or family care, or who are self-funding but not using council-arranged care."
Fears were also raised that the government's share of the total estimated bill towards free care – £420m – will be funded by cutting large sums from the Department of Health's research and development budget.
Health secretary Andy Burnham insisted the bill is a bridge towards a national care service and insisted the money will not come from cutting disability benefits or from cutting cancer research or any other important research.
The legislation is intended to be the first step towards establishing a National Care Service.
The bill does not apply to Scotland, where there is free personal care for older people, and the UK government will seek the Welsh Assembly's agreement on the plan being applied in Wales.
Cost of free personal care higher than claimed, say councils
Free personal care: elderly people want eligibility answers
Free personal care bill published today
DH denies dementia research at risk from free care
Free home care plan to exclude some with critical needs