Gordon Brown has warned that senior Conservatives are "testing the water for a different kind of NHS" which could see the public charged for some services.
The former prime minister hit out following a claim by Sajid Javid that patients should pay a fee for visiting GPs or A&E wards.
Javid, a former UK health secretary, claimed in an interview last week the NHS could not "survive much longer" without radical change including introducing patient charges.
Brown, who stepped down as Labour leader in 2010, warned "the direction in which the Conservatives are travelling is already clear".
"Javid, a former chancellor and health secretary, has written approvingly of the £20 fee that some European countries charge for visits to the GP," he wrote in a column for the Guardian.
"He labels Ireland’s €75 (£66) bill for attending an A&E without a GP’s referral as merely 'nominal', as if it’s so modest that a higher charge would be more appropriate. And he calls for a national debate on the contribution private financing can make to healthcare.
"But the direction in which the Conservatives are travelling is already clear. The sick would pay for being sick and charging would force, as has happened with GP and hospital fees in France, the better-off sections of the population to take out private insurance – inevitably creating, in its wake, a two-tier healthcare system."
Brown added: "Javid’s intervention is no accident.
"The prime minister, Rishi Sunak, who has used private healthcare, once came up with a proposal for new charges: £10 for patients who miss GP and hospital appointments. And so once again, as they did in opposition at the turn of this century, with Alternative Prescriptions, Conservatives are testing the water for a different kind of NHS."
The NHS in Scotland is the responsibility of Holyrood but a row over its future has been raging for months as A&E wards struggle to meet demand.
Humza Yousaf, the SNP health secretary, was last year forced to insist the health service would stick to its "founding principles" and will not start charging patients for treatment.
The under-pressure health secretary spoke out after a leaked document revealed senior bosses had debated the creation of a "two-tier system" which could see wealthier Scots asked to pay.
The minutes were compiled from a meeting in September given the "green light" by NHS Scotland chief executive Caroline Lamb to discuss reform of a service which finds itself in crisis.
Yousaf said: "The Scottish Government’s policy could not be clearer, our National Health Service must be maintained to the founding principles of Bevan – publicly owned, publicly operated, and free at the point of need.
"The provision of health services must always be based on the individual needs of a patient – and any suggestion that this should in some way be based on ability to pay is abhorrent."
To sign up to the Daily Record Politics newsletter, click here.
