Prominent Tory backbench Jacob Rees-Mogg has urged the Government to spend the "Brexit dividend" on the NHS ahead of the Chancellor's spring statement.
In an interview on Peston On Sunday, Mr Rees-Mogg warned it was not realistic to expect the current levels of funding to be maintained.
He said there had been a "significantly lower real-terms increase in health spending" since the Tories came into power compared to the last time the party was in government, and that the Brexit dividend should be spent on health services.
"I would like to see the dividend of leaving the European Union devoted to the health service," Mr Rees-Mogg said.
"I think people felt that was promised during the referendum campaign and the figures on health spending, in real terms since 2010, is a 1.1% increase.
"Whereas in the period of the Conservatives in government from '79 to '97, it was 3.4%. So we're running at a significantly lower real-terms increase in health spending currently.
"And with an aging population, with increasing medical sophistication, I don't think it's realistic to expect that the current levels of spending can be maintained."
It remains to be seen how much money Britain will save by leaving the EU, with leaked economic reports showing Brexit will leave the UK worse off no matter what future deal is struck with the EU.
It is also likely Britain will continue paying into the EU budget until the end of 2021.
Later on the programme Chancellor Philip Hammond stressed that Tuesday's spring statement was "not a fiscal event".
"As we come to the Autumn budget, if we at that point we have some fiscal capacity, some headroom available, we will use it as we used headroom at the autumn budget last year, in a balanced way," he said.
"We've got to keep reducing the deficit so that debt falls, but we've also got to support our public services, we've got to reduce taxes so that people keep more of the hard-earned money they earn and we must keep investing in Britain's future - infrastructure and skills."
Mr Hammond also warned he will not relax his grip on the public finances, saying Britain's debt mountain was still too high and had to be be brought down.