"In effect, this policy change will create a class system for health care in Canada," Matthews wrote.
The Interim Federal Health Program gives temporary health-care coverage to approximately 128,000 refugees. Some physicians say drastic cuts to the IFHP will leave some government-assisted refugees vulnerable.
Kenney has responded to protesting doctors and refugee advocates by saying what's being eliminated is not basic care but services that other modest-income Canadians also have to pay for.
Matthews writes that the government is "abdicating your responsibility towards some of the most vulnerable in our society" and downloading federal costs on to the provincial health-care system.
"Even in emergency circumstances, your changes will see certain refugee claimants receiving no health-care coverage at all," she wrote.
"Should a refugee claimant suffer a heart attack, your government will now refuse any health-care coverage. It is grossly irresponsible to withhold funding for this care in a life-threatening situation.
"Ontario's health care system will not turn away those in need of emergency medical treatment," she added.