A collapse in Conservative support across the southwest of England could see the party lose 11 seats in a general election – and come within a hair’s breadth of losing the constituency of Jacob Rees-Mogg.

YouGov found that Tory vote share in the seats which they dubbed the “Conservative Celtic fringe” has dropped a remarkable 19 points since the 2019 general election, leaving Boris Johnson’s party on 38 per cent in the region.

The figures were released on the day of a by-election in the Devon seat of Tiverton and Honiton, where Liberal Democrats are hopeful of overturning a massive Conservative majority in an area which has been “true blue” since 1923.