Johannesburg - Inkatha Freedom Party MP Mario Oriani-Ambrosini died on Saturday after battling cancer, his family said.
"It is with deep sadness that we, the family of Dr Mario Oriani-Ambrosini, advise of his passing in the early hours of this morning, after a long and courageous battle with terminal lung cancer," they said in a statement.
"We wish to thank everyone who offered such tremendous support over the past 19 months."
The family said the love and warmth shown to Oriani-Ambrosini and to them from friends was appreciated.
Oriani-Ambrosini announced last year that he had been diagnosed with stage four lung cancer.
At the time, he said his doctors did not expect him to see Christmas 2013.
Oriani-Ambrosini said he had rejected chemotherapy as a treatment option, as it would extend his life expectancy by only a few months and would cause severe side-effects. He had opted to pursue treatment based on "different science".
In February this year, he tabled legislation to decriminalise the medical use of dagga.
Oriani-Ambrosini, who had just returned to the National Assembly after months of absence, made an impassioned plea to President Jacob Zuma and his government to decriminalise "medical marijuana".
His family said he had many battles in life but his battle with cancer was his toughest.
"Nonetheless, he continued to fight, not only for his own sake, but on behalf of the countless people who face this same battle.
"His contribution to the fight against cancer will be remembered forever with appreciation and his work will be continued through the Cancer Treatment Campaign, which he started early this year," the family said.
Funeral arrangements would be announced in due course.