GPs have been accused of blocking patient choice by a health minister.
A look at why this is a contentious issue and what might change.
What have doctors been accused of?
In an interview with the BBC website, Health Minister Ben Bradshaw said some family doctors were operating "gentleman's agreements" whereby they refuse to accept other GPs' patients.
He believes doctors are carving up areas so that if a patient wants to register with a practice they will only be allowed to do so if they live within a certain distance.
If they do not, he believes doctors are saying their lists are full when officially they are not classed as such.
The government says they have been alerted to the problem by primary care trusts that have been forced to find alternative services for patients.
But doctors reject the accusations, saying such agreements do not exist and where patients cannot register it is because lists are full and resources stretched.
Does this matter?
The government says patient choice is important because it creates competition between GPs.
Ministers say this in turn improves standards - just as has happened with hospital care where patients can choose from any hospital in the country for elective treatment.
And it is all part of the government's wider plan, spelt out by the review of the NHS by Lord Darzi earlier this week, to create a more personalised health service.
Although, GPs are less convinced of the merits. They say competition goes against the culture of the profession.
They also claim spending time and money on marketing themselves to patients would be a waste.
How does the government want to change the system?
Ministers say the key is tweaking the way practices are funded. GP pay is broken down in two separate parts - basic pay and a bonus element.
The basic pay for most doctors includes a lump sum and money for each patient registered with them.
The bonus part is for hitting performance targets and providing extra services.
The government believes that by phasing out the lump sum more money could be attached to the numbers of patients registered with the practice.
This would then incentivise doctors to push to get more patients.
Talks have already started and the doctors' trade union, the British Medical Association, is not opposed to phasing out the lump sum.
But it wants to see the amount of money invested in GPs increase.
Haven't doctors and ministers clashed before?
Yes. This is just the latest in a long line of clashes. In many respects, it is all related to the new contract that started in 2004.
In the first two years of the deal, GPs saw their pay rocket and break through the £100,000 a year barrier.
Amid mounting criticism, the government has sought to get more and more out of GPs.
Ministers have already forced many of them to open for longer in the evenings and at weekends and are now turning their attention to widening choice.
GPs are clearly angry about what they see as an unfair campaign against them.
They point out that the large income rises were followed by two years of pay freezes, leaving the profession desperately short of resources.