Ed Miliband is demanding the prime minister should "come clean" over accusations that he is planning a drive for more privatisation of the health service if he is returned to Downing Street.
In a campaign visit to Brighton, the Labour leader will call on David Cameron to admit the Conservatives' plans for the NHS as the party highlights a report on health service reform by former Marks and Spencer boss Stuart Rose, now a Conservative peer, that has been left unpublished.
Miliband will be joined on the south coast by shadow chancellor Ed Balls and celebrity chef Delia Smith who has given her backing to the party because of her concerns about the future of the NHS.
Miliband is expected to say: "In the final few days of this General Election, the future of the NHS is at risk in the way it hasn't been for a generation.
"We know that if David Cameron wins a second term there will be a drive for more privatisation, more broken promises and more people waiting longer for treatment.
"In this election, you have the chance to put the NHS first by voting Labour on Thursday. There is no bigger choice at this election than the future direction of our National Health Service, the bedrock of security for so many working people in our country.
"But our NHS is in huge danger. It's fighting for its life because of choices this Government has made."
The future of the NHS has been at the forefront of the election campaign as the parties seek to convince voters they will protect it.
Conservatives and Liberal Democrats have pledged they will find the £8 billion health chiefs say is needed by 2020 to prevent it buckling.
Labour has refused to commit to providing the same amount but insists it will do "what is necessary" and says its £2.5 billion spending plans are the only fully-funded proposals put forward so far. It claims the Tories want to open up the service to greater privatisation.
Lord Rose was asked to lead a review into how to improve management in the NHS in England last year and reported back to the coalition but his findings have yet to be published.
The Labour leader will also promise to repeal the coalition's Health and Social Care Act.
"I know what makes the NHS strong: care, compassion and co-operation, not privatisation, fragmentation and competition.
"So in our first 100 days we'll put before Parliament a bill to repeal the Tories' terrible Health and Social Care Act, stopping the drive towards privatisation. And where private companies are involved in delivering NHS-funded clinical services, we will cap the profits they can take out of the public purse."