The Liberal Democrats would refuse to form a coalition with either of the main parties while they are “dragged off to the extremes”, the favourite to be their next leader has said.

Jo Swinson said she could not envisage a coalition with Labour or the Conservatives after an extraordinary YouGov poll for The Times showed that her party has surged into first place ahead of both big parties and the Brexit Party.

The pro-Remain party topped the survey with 24 per cent, the first time it has been in the lead since 2010 under Sir Nick Clegg’s leadership. With the Brexit Party second on 22 per cent, it is the first time since polling began that neither Labour nor the Conservatives have appeared in the