He passed away this morning at the age of 90.
Late last month, Sir James was flown to the Queen Elizabeth Hospital in Barbados for medical treatment after falling ill in his hometown of Bequia, St Vincent.
He had been diagnosed with dengue and other health conditions.
Sir James became a parliamentarian at age 35. He founded the main opposition New Democratic Party (NDP) in 1975.
Sir James, an agronomist, was Prime Minister from 1984 to October 2000.
More details to come.