The dispute over Canada’s involvement in the US presidential race took a new turn on Thursday as Hillary Clinton’s campaign and the Canadian government both fended off allegations that Mrs Clinton’s staff had told Ottawa not to worry about her stance on the North American Free Trade Agreement.

Reporters at CTV, a Canadian television network, said a senior Canadian official had told them in a casual conversation last week that Mrs Clinton’s campaign had assured the Canadians that her promise to renegotiate Nafta should be taken “with a grain of salt”.