"I didn't come into politics to make the lines on the graphs go in the right direction," Cameron will say, according to extracts of his speech in comments designed to address criticism that his centre-right party prioritises deficit reduction over social security issues.
Opinion polls show that the future of Britain's internationally-renowned National Health Service (NHS) is a key issue for voters, and that the opposition Labour party is more trusted to protect the service than the Conservatives.
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Cameron will attempt to claw back some ground on the issue with a pledge to increase the NHS budget and insulate it from the drastic cuts faced by other government departments over the coming years as part of the drive to balance Britain's books.
"The next Conservative government will protect the NHS budget and continue to invest more," Cameron will say.
The speech will look to frame the fate of the NHS, which is predicted by some to face a long-term funding shortfall due to Britain's ageing population, as an economic issue on which his party can be trusted, while the opposition Labour party cannot.
"We know this truth, something Labour will never understand and we will never forget: you can only have a strong NHS if you have a strong economy," he will say.
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The Conservative party lags Labour in overall opinion polling going into what is expected to be a close election race, but ranks much higher than the centre-left opposition when voters are asked about economic competence.
Healthcare, which is free at the point of delivery, currently accounts for one in every seven pounds of government spending and has been protected from cuts since Cameron took power in 2010. He did not specify how much the promised real term increase in spending would amount to.
Last week, Labour announced plans for a 2.5 billion pound spending injection for the NHS funded by a tax on high-value homes and a levy on tobacco firms.
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They say that the Conservatives cannot be trusted to run the health service, blaming them for job losses and what they argue are declining service standards.
Cameron's decision to protect the healthcare budget from planned spending cuts - a process known as ringfencing - is likely to draw criticism from experts who have already expressed fears that the practice magnifies the impact of spending cuts on other already-squeezed departments.
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