The Ontario Medical Association is suing the Ontario government over recent reductions in fees paid to the province's doctors.
The physicians lobby group launched a constitutional charter challenge on Thursday, saying the latest cuts will compromise patient care across Ontario.
The government has cut funding for physician services by a total of 6.9 per cent since February in what Health Minister Eric Hoskins has described as a bid to free up money for other health services.
Hoskins argues that Ontario's doctors are among the best-paid in the country with an average salary of more than $358,000.
But the OMA's challenge asserts that the fee cuts are unfair to doctors and risk leaving patients without necessary care.
The association is asking the court to declare that physicians have a constitutional right to a binding dispute mechanism for disputes over compensation issues.