In a book on the sovereigntist movement to be published on Monday, the former premier of Quebec, Jacques Parizeau, writes that had the "yes" camp triumphed in Quebec's October 1995 referendum on independence he would have made a unilateral declaration of independence within days. It would have triggered a constitutional crisis between the mainly French- speaking province of 6.5 million people, and the 19 million mainly English- speaking people of the rest of Canada.
The confession has electrified the election campaign which closes with polling on 2 June. It will also serve to ensure that the single issue that has haunted Canadian politics for the past two decades - the future of Quebec - will once more dominate the election trail.
For leaders of the Bloc Quebecois, who are fighting to retain their dominance of the province and to build momentum for yet another referendum, the book is an acute embarrassment. Its leaders moved yesterday to dissociate themselves from the UDI claim. Lucien Bouchard, the current Quebec Premier and the sovereigntist movement's figurehead, swiftly tried to limit the damage. He told reporters that had he had knowledge of the plan "I would have to disassociate myself from it".
Mr Parizeau was forced to resign his leadership of the Parti Quebecois, the pro-sovereigntist ruling party in Quebec, immediately after the 1995 vote. The book's revelations are stunning, in particular, because he had signed an agreement with other party leaders only months before the referendum agreeing that a "yes" vote for sovereignty was to be followed by a year of negotiations with the rest of Canada for an amicable divorce.
Mr Parizeau says he was secretly engaged in a "great game" to engineer the fastest possible rupture of Quebec from the Canadian federation. He said it was conceived on the advice of the former French president, Valery Giscard d'Estaing, whom he visited, in France, at the start of 1995. He allegedly encouraged Mr Parizeau to believe that UDI by Quebec would be rewarded quickly by recognition of the new nation from Paris.
Mr Giscard reasoned that the nod from Paris would then be followed by a similar act of recognition from Washington. But it is not clear, however, whether Mr Parizeau received any official encouragement from the French government itself.
"It was during this trip that Valery Giscard d'Estaing raised a question of which I had not, until then, understood the significance," Mr Parizeau writes. "It is essential, he said in essence, right after the referendum, in the hours or days that follow that there be a solemn gesture taken by Quebec to proclaim its sovereignty. Without that, no quick recognition, that is to say in a week or ten days afterward, will be possible on the part of a foreign country."
For Jean Chretien, Canada's Liberal Prime Minister, the remarks are a gift from heaven. Speaking to supporters in Quebec City on Wednesday, he said: "We learnt today how the Bloc and their allies tried to fool Quebecers. I deeply believe that Quebecers deserve the truth and the whole truth."