Labour leadership candidate Owen Smith has accused the Tories of having a "secret plan to privatise the NHS" ahead of a major speech on the health service.
It will be delivered amid continued infighting between Jeremy Corbyn and his elected deputy, as the battle for control of the party grows ever more intense.
Mr Smith will cite Department of Health (DH) figures showing that £8.7 billion was spent on buying healthcare from the private sector in 2015/16 - or 7.6% of total spending and more than double the amount when the Tories took power in 2010.
It comes after confirmation that his leadership contest with Mr Corbyn will continue with the exclusion of around 130,000 new members, many of whom are believed to support the incumbent leader.
The row between Mr Corbyn and Tom Watson over the deputy leader's claims that "Trotsky entryists" were infiltrating the party also rumbled on.
Mr Watson presented what he claimed was fresh evidence showing hard-leftists were attempting to join Labour and manipulate young members to boost support for Mr Corbyn.
Mr Corbyn has accused Mr Watson of talking "nonsense" over the claims.
But on Sunday night the deputy leader posted what he said was fresh evidence of entryism on his Facebook page, adding in a statement: "I know Jeremy is very busy on the campaign trail and is therefore relying on others to tell him what I have said.
"To repeat again, I have never said that all our new members are Trotskyists. I have never claimed that hundreds of thousands of new joiners are revolutionary socialists and those who claim I did are attacking a straw man.
"I simply want to ensure that organisations like the Alliance for Workers Liberty, who have instructed all their members to join the Labour Party and target our youth sections for recruitment, are dealt with under our rules. It's undeniable that this is happening. AWL even published these instructions on their website."
Steering clear of the row, Mr Smith will accuse Health Secretary Jeremy Hunt of "covering up" the scale of NHS spending on the private sector, after 2014/15 figures were revised up from initial estimates by more than a billion.
And he will highlight recommendations made by the regulator set up by Mr Hunt, NHS Improvement, which say private providers are being "under-utilised".
Commenting before the event in Salford, Greater Manchester, Mr Smith said: "It is now clear that Theresa May has given Jeremy Hunt the green light to start privatising our health service.
"Within days of his reappointment as Health Secretary he had officials drawing up secret plans to privatise the NHS.
"Like many families across Britain my family is relying on the health service at this very moment.
"The NHS is our country's most valued institution, and people will be shocked to hear that the Tories have been putting together a secret plan to privatise it.
"We all rightly contribute to the NHS through our taxes, but we must make sure that money is spent on doctors and nurses, and not lining the pockets of private sector shareholders.
"It just goes to show you can't trust the Tories with our NHS. Under their rule it is in crisis yet again, with waiting lists growing and hospitals dangerously understaffed."
Mr Smith added: "As prime minister, I would call an immediate halt to Tory privatisation, set about scrapping the Tories damaging health reforms and make sure our NHS has the cash it so desperately needs - boosting spending by at least 4% every year."
The speech comes after five of the 130,000 members excluded from voting in the race dropped their legal challenge against the decision of Labour's ruling body to bar them from voting because they had not joined the party by January 12 and held membership continuously until July 12 - the "freeze date".
Those affected were given an opportunity to vote by paying an extra £25 to become "registered supporters" but the five insisted that was wrong and took their fight to the courts.
After the Court of Appeal overturned an initial victory, they dropped their case, citing increasing costs as the reason for not taking their battle to the Supreme Court.