David Cameron has admitted that even his brother-in-law, who is a doctor, has cast doubt on the Government's plans to reform the NHS.
The medic, who works in a hospital, has expressed concerns that hospitals would lose out under the shake-up, he said.
Discussing the plans with a doctor and patient in a consultation at a health centre, the Prime Minister told them: "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'."
Mr Cameron's brother-in-law, Dr Carl Brookes, is a cardiologist at Basingstoke and North Hampshire NHS Trust. He is married to the Prime Minister's sister, Tania.
The proposals, which centre around handing GPs £80 billion of the NHS budget and increasing the role of private companies in health provision, have come under fierce criticism from unions and clinicians in recent weeks.
But local GPs talking them over with Mr Cameron during his visit to the St Charles' Centre for Health and Wellbeing in Kensington, west London, were broadly in favour. The Prime Minister put it to them that hospital doctors might consider them unfair, but Dr Mark Sweeney, who is head of the local GPs' consortia, said GPs and hospital doctors would "work together rather than against each other".
The GPs also expressed support for the idea of working with the private and voluntary sectors, telling Mr Cameron, Health Secretary Andrew Lansley and local MP Sir Malcolm Rifkind that they welcomed the opportunity.
The discussion came after Mr Cameron warned earlier that the NHS would become "increasingly unaffordable" if the radical plans were not implemented.
Insisting that the "biggest risk" to the NHS would be to do nothing, he told BBC Breakfast: "If you look at the growth of the elderly population, look at the new drugs that are coming on stream, the new treatments, if we keep the system we have now and don't make changes to cut bureaucracy and waste, I think it will become increasingly unaffordable."
Meanwhile, protesters opposed to the reforms planned to demonstrate outside Parliament as ministers begin a second debate on the controversial Health and Social Care Bill.