Mayor of London Boris Johnson, who is also a Conservative, told BBC One's Andrew Marr Show, that while he was "not going to say the election is a done deal... it is like a novel where the denouement has become obvious a little bit too early".

He said: "I think the Labour government is almost completely discredited. In my view they have bogged it up in the most imperial, inter-galactic fashion. They have run up colossal sums of debt and have no credible way out of it."