The WhatsApp rebellion: ex-minister Steve Baker rallies Brexit hardliners against UK PM Theresa May

British Prime Minister Theresa May faces a concerted rebellion from the hard Brexit wing of the Conservative party on Monday, as MPs unhappy with her Chequers compromise prepare to mount a show of strength by voting for their amendments on a crucial customs bill.

The party’s European Research Group says it will reject any last attempts at compromise by Number 10 as they hope to force May to change course over Brexit or risk a no-confidence vote before the summer break by demonstrating the depth of their support.

A special ERG whipping operation, using the WhatsApp messaging service, has been created by Steve Baker, a former Brexit minister who resigned from the government last week, although ERG insiders would not put a number on how many they expected to rebel in the Commons.

Jacob Rees-Mogg, the chairman of the ERG, told the BBC “we’ll have an idea of the numbers at 10pm on Monday evening” while one ERG insider added that they were “intensely relaxed” about the number of rebels they had signed up.

Last week, members of the hard Brexit group put down four amendments to the taxation (cross-border trade) bill due to be debated on Monday evening, aimed at halting the customs plan announced by May at Chequers nine days ago.

The level of support they attract will draw intense focus, particularly if the number significantly exceeds the 48 required to call for a vote of no confidence in May’s leadership of the Conservative party.