Ringfencing the £100bn NHS budget would be of limited value, according to the new chair of the health select committee Stephen Dorrell.
The former Tory health secretary said a radical voucher plan for patients to buy treatments would be a better option.
Speaking before the launch of a report by the 2020 Public Services Trust think tank, called Improving Health Outcomes, Mr Dorrell said that it was "inescapably true that plans to increase spending on the NHS in real terms year on year would mean cuts in other services such as social care and housing, both of which will have an adverse impact on health".
According to the think tank, of which Mr Dorrell is a commissioner, it would be economically unsustainable to ringfence the health service budget because "societal challenges ahead, such as the ageing population, will cost an extra £300bn by 2025".
Mr Dorrell said the strength of public feeling over the NHS had made the coalition promise to increase health budgets in the short term.
According to a poll, 82% of people believed the NHS should be a priority area for protection.
Mr Dorrell said the extra money should be used to get "real reform" within the NHS, and to build good relationships with clinical staff who might otherwise frustrate attempts to bring about change.