As many as one-tenth of GP practices are expected to close in Northern Ireland this year, a doctors' union warned.
Dr Tom Black called for an additional investment of £120 million in general practice. Reform has been delayed by the collapse of Stormont powersharing.
The senior medic warned when 60% of doctors signed undated resignation letters they would decide on whether to leave the NHS.
He said: "The NHS in Northern Ireland is in its greatest crisis since its inception."
Dr Black is the chairman of Northern Ireland's GP Committee (NIGPC) and addressed a conference in Edinburgh.
He said: "We expect to lose between 5 and 10% of GP practices this year and we have already lost more than a quarter of GP practices in County Fermanagh so far this year."
Dr Black said plans for reform were agreed before Christmas with civil servants and the previous health minister.
Following the collapse of the powersharing negotiations and lack of an agreed budget, the future of Northern Ireland's healthcare system has been left shrouded in uncertainty.
Dr Black added: "We cannot stand by and watch the destruction of the general practice through neglect, prejudice and incompetence.
"We have found that the only thing worse than having politicians is having no politicians."
He said Northern Ireland patients endured the longest waits for secondary care in the UK, five and a half years for a hip operation.
"General practice is in an existential crisis with the highest workload, the smallest workforce and the lowest funding per capita of any of the four countries.
"This is a recipe for collapse and we're seeing this in all six counties."
A "plan B" of options for dealing with the crisis is due to be distributed by the British Medical Association (BMA) in Northern Ireland to GPs this summer.
Dr Black added: "GPs in Northern Ireland are imbued with the values and principles of the NHS and do not want to leave the NHS to adopt private practice provision under Plan B.
"GPs in Northern Ireland want to stay in the NHS and work under Plan A where patients receive a universal service, free at the point of need, funded by taxation.
"Unfortunately, however, at the moment it looks like it won't be a choice between an NHS service or a private GP service.
"It looks like it will be a choice between an absent collapsed GP service and Plan B alternatives."