Helen Whately, deputy chairwoman, said the local elections were “going to be a difficult night for us”

Theresa May is set to suffer the worst set of local election results for a Conservative government in more than 20 years.

The party will lose 800 councillors compared with results four years ago as voters punish it for the Brexit deadlock, according to a projection.

Lord Hayward, a Conservative peer and leading local elections expert, believes Labour could pick up 300 seats and the Liberal Democrats 500.

Tory losses are particularly acute because in 2015 the party put in a relatively strong performance, with the local polls taking place at the same time as David Cameron’s victory. For the same reason, Labour and the Liberal Democrats’ recovery is flattered by coming from a low base.

Lord Hayward said: “The Tories are at an historic