Payment for NHS treatment may need to be considered as part of a new settlement on funding the care and support of Britain's ageing population, according to the peer who chaired the royal commission on long-term care in the early days of the Blair government.

Lord Sutherland, whose commission saw its recommendations shelved in England but later introduced controversially in Scotland, says the imperative to find more funding for care and support of elderly people should force a review of all forms of public spending and a redistribution of priorities between social care, health, housing, welfare benefits and other services.

"Whether you have Alzheimer's, or lung cancer or a bad liver, you should get equity of treatment within the system," Sutherland said in an interview with the Guardian to mark 10 years since the publication of the commission's report. "If you have got to pay 10% of it, you pay 10% across the board.

"I think this is the way it's going to go because this particular group, the old, is getting bigger and more vocal. If we're told we can't afford equity any other way, I think it would be a fairer system."

The Westminster government rejected most recommendations of the Sutherland commission because its central proposal for free personal care, such as the washing and dressing of elderly people, was considered too expensive. The policy was introduced in Scotland in 2002, but has run into problems and the Scottish administration is this year injecting an additional £40m to support it.

Sutherland said he thought the policy had bedded in well north of the border, despite teething troubles, but none of the three main English political parties now backs free personal care.

The Brown government is drawing up a green paper for launch this spring on options for reform of the funding system. These will range from compulsory care insurance to simply adjusting the existing rules, under which people must contribute to their care and support costs if they have assets of £22,500 or more – even if it means selling the family home.

Sutherland, a crossbench peer and former academic who led the goverment's recent review of the fiasco over the marking of Sats tests last summer, said a lasting reform of care funding might have to involve addressing the widening gulf between the £100bn-a-year NHS and the £12bn-a-year social care system.

"Yes, they should be in the same bucket," he said, "and a view taken about what we as a nation not just can afford, but want to afford. There are choices here."

The charity Counsel and Care called on ministers yesterday to look at how inheritance tax could help meet the costs of a reformed care and support system.

Stephen Burke, the charity's chief executive, said a "care duty" of 4.25% levied on estates could generate £3bn, or 2.5% could raise £1.7bn. "The growing care funding gap needs to be addressed urgently."