The Clinton campaign lashed out at the director of the FBI over the weekend after news that it was investigating a further batch of emails upended the US election campaign as it headed in to its final full week.

FBI director James Comey’s shock disclosure that his agents are seeking court approval to review newly discovered emails from Huma Abedin, one of Hillary Clinton’s closest aides, looks set to dominate the final days of the campaign.

It comes amid signs the race was already tightening. An ABC News tracking poll released on Sunday showed Mrs Clinton clinging to a one-point lead over Mr Trump, 46-45, in a four-way showdown that included the Libertarian and Green party candidates. The poll, a rolling four-day average, had Mrs Clinton up by a dozen points just one week ago.