Frank’s Law would cost the public purse less than £100m a year, according to an independent estimate.
Miles Briggs, the Conservative MSP, lodged a bill last week to abolish care charges for under-65s with debilitating illnesses.
The new shadow health secretary has used Scottish Parliament Information Service figures to predict the price of closing the loophole at between £40m-£100m a year.
Mr Briggs said he is confident the outlay would be nearer to the lower end, adding it is a reasonable sum for ending age discrimination.
“This isn’t going to break the bank,” he told The Courier. “There will also be financial benefits from those receiving care and not having to rely on acute settings later on.
“It’s about preventative measures and it’s also about ensuring people are treated fairly.”
The campaign, which is fought in the memory of Dundee United legend Frank Kopel, calls for under-65s with conditions such as dementia to be given the same rights to free care as older people.
Backed by The Courier, it has been led by Frank’s widow Amanda and has attracted the support of all opposition parties at Holyrood.
A senior SNP source told The Courier last week that the loophole will be closed.
He said: “Be in no doubt – the SNP will deliver Frank’s Law – it’s going to happen.”
Alex Neil, the Nationalist MSP and former health secretary, declared his support for the move last week.
The Sunday Times reported senior sources in the Scottish Government were signalling caution over affordability.
The source said: “The affordability of this scheme…is one of the key criteria in assessing whether this will go ahead. There will be rigorous examination of how many people will be entitled to the extension of the benefit and how it can be delivered.”
If the scheme cost £70m that would represent 0.2% of the total Scottish budget.
The Scottish Government expects a feasibility study into extending free personal care to be completed in the summer.
Officials have already asked councils to cost the plan, a move which has buoyed campaigners.
A consultation on Frank’s Law is due to start this week.