David Cameron has been defending his health service reforms against charges that they represent a gradual privatisation of the NHS.
But embarrassingly for the Prime Minister, he admitted a member of his own family had reservations about his plans while visiting a London hospital.
"My brother-in-law is a hospital doctor and he says 'You're giving too much power to the GPs, and hospitals will be disadvantaged'," he told a patient.
As MPs prepare to debate the Health and Social Care Bill, and as unions prepare to protest outside parliament, Mr Cameron argues that the reforms are essential.
The Prime Minister, in a letter to The Times, argues that without modernisation, the NHS will become unaffordable.
"Fail to modernise, and the NHS is heading for crisis," he writes, claiming that the Coalition government's proposals are simply about using more efficiently and effectively what already exists.
"GP-led commissioning, patient choice, payment by results and Foundation Trusts have all existed in one form or another over the past 15 years," he continued.
"The NHS has always worked with a range of social enterprises, charities and private companies. The difference is that we plan to make these changes effective right across the NHS."
Health unions, however, say the greatest threat to the NHS is the reform programme itself.
They claim most people oppose it, including many GPs, patients, clinicians, charities and MPs - who are also concerned that the Government is trying to rush through a complex Bill containing 280 clauses without sufficient scrutiny.
The public sector union UNISON conducted a survey of 2,000 adults which the union said revealed that 56% of Liberal Democrat voters oppose private firms providing NHS services, while only 46% of Conservative supporters support the move.
The Royal College of Surgeons has warned that patient care could be compromised if GPs, who would control £80bn of the NHS budget, start to focus on price rather than quality.
In the Commons, there is disquiet, once again, among Lib Dem MPs, and even some Conservatives are worried that the reforms might prove damaging.
Mr Cameron and his Health Secretary Andrew Lansley should be able to steer the Bill through parliament, but then the true test will come, with the health unions warning of dire consequences, no less than the destruction of the NHS as a universal service free at the point of delivery.
Health workers are expected to stage a protest outside Parliament during the debate.