The phrase "foremost proponent" is correct and can be used in written English.
It is commonly used to refer to someone who is the most influential or dedicated supporter or advocate of something. Example: As the foremost proponent of environmental conservation in our community, Jane has organized multiple successful cleanup events and initiated several recycling programs.
Peres is Israel's greatest optimist, its foremost proponent of what he has termed "the new Middle East".
He was also the foremost proponent of sociobiology, the study of the genetic basis of the social behaviour of all animals, including humans.
He was a foremost proponent of Jewish education and other Jewish values which he and Ann inculcated into their entire family.
According to Frank Kitson, the British army's foremost proponent of counter-insurgency tactics: "Everything done by a government and its agents in combating insurgency must be legitimate.
The disaster will also put pressure on the German chancellor, Angela Merkel, the foremost proponent of openness towards refugees, to shift her position.
The shooting death of the nation's foremost proponent of nonviolence helped spur Congress to pass the Gun Control Act of 1968.
The two men, along with Thomas Keller of French Laundry in California, are popularly considered to be the foremost proponents of "molecular gastronomy".
Throughout his career, and particularly in recent years, he's shown himself to be among the foremost proponents of these values.
In Mr Rumsfeld, he chose one of the country's foremost proponents of that system, which grew partly out of the alarming findings of the Rumsfeld commission into the threats of "rogue states".
Its foremost proponents include Eric Ries, an engineer, entrepreneur and author who coined the term and is now an entrepreneur in residence at the Harvard Business School, and Steven Blank, a serial entrepreneur, author and lecturer at Stanford.
British architect who, with his wife, Alison, was among the foremost proponents of the New Brutalism style of architecture, which stressed a new respect for the functionality of materials.
