The Canadian government has refused entry to Mr Ruairi O Bradaigh, leader of the splinter republican group, Republican Sinn Fein, whose party is opposed to the current IRA ceasefire.
Mr O Bradaigh was not allowed to board a charter flight to Toronto at Shannon Airport. He was informed that permission for his entry to Canada was refused by the Canadian High Commissioner in London, a spokesman for Mr O Bradaigh said.
Last year, the US government refused Mr O Bradaigh entry to the United States, also on the grounds of his party's refusal to accept a ceasefire.
In a statement yesterday, RSF said Mr O Bradaigh was on his way to Toronto to attend a 150th anniversary commemoration of the Irish Famine at Grosse Ile on the Lawrence River. It said the refusal of entry was "an abuse of" Mr O Bradaigh's rights.