Butler, who moved with her family to Canada when she was 10, has also received approval from UK Athletics to make the move. It means she will be able to compete in the colours of the country of her birth in the Sydney 2000 Olympic Games.
Butler, fourth in this year's World Cross Country short-course race and a regular on the international circuit since 1990, has become disillusioned at the lack of funding for sport in Canada, whereas as a British national she would immediately become eligible for lottery funding.
Brent McFarlane, head coach of Canada's 2000 Olympic team, said: "It's a dark day for Canadians when we lose such an outstanding young lady and athlete to another country because we do not have the government financial support. We should all be asking ourselves and local politicians why this has happened."
The Senegalese lawyer, Lamine Diack, has been temporarily installed as president of the International Amateur Athletic Federation following the death of Primo Nebiolo due to a heart attack on Sunday. Under the IAAF constitution vice-president Diack, 66, who was the French long jump champion from 1957 to 1960, is in charge of the world governing body, but no provision has been made to elect a new president. Nebiolo was re-elected by acclamation for a further four-year term at the IAAF congress in Seville in August.
Dozens of mourners filed past Nebiolo's casket yesterday in the shadow of a fresco portraying Roman emperors at the Italian National Olympic Committee headquarters in Rome. Two of the room's walls are covered with Fascist-era murals, depicting Imperial Rome and Mussolini marching on the city. The other walls have posters representing each of the modern Olympic Games.