Conservative activists could go on strike and refuse to campaign for Tory MEP candidates after Theresa May said the UK will prepare to take part in European elections on May 23.

Mrs May asked the European Union on Friday to delay Brexit to June 30 but said she wanted Britain to have left with a deal by May 22.

However, she admitted staying in the bloc beyond that date would require the UK to elect new representatives and as such was triggering preparations which she hoped ultimately to cancel.

Her decision sparked widespread fury among Tory Brexiteers who said it would be “crazy” for people to be asked to elect a fresh batch of MEPs almost three years after voting to leave the EU.

Pro-Brexit campaigners and hardline Eurosceptics predicted the Conservatives and Labour Party would face a “seismic electoral backlash” if Britain did take part.

Meanwhile, pro-European parties like the Liberal Democrats welcomed potentially contesting the elections because they believe millions of Remain voters will mobilise behind them.