The pressure is beginning to mount on British Prime Minister Theresa May to resign after the pro-Brexit Speaker of Parliament, Andrea Leadsom, quit after saying she no longer believes the May government can deliver on the UK’s withdrawal from the EU.

A spokesman for May said the government remained “focused on delivering Brexit.”

Leadsom, who ran against May for the leadership of the Conservative party and may be harbouring ambitions to succeed her. She has grown particularly sceptical towards May after the divisive prospect of a second referendum and a fourth attempt at passing the Withdrawal Agreement with Brussels remained on the table.

Conservative backbenchers have been threatening a revolt since May reached out to Labour, offering a Customs Union and the prospect of a second referendum. To her own backbenchers, May offered the ill-defined legally binding deadline of reaching a deal that would resolve the border issue between EU-member Ireland and Northern Ireland, which will remain in the UK.

If the polling is correct, the Conservative Party will come out in fifth in this week’s European elections. May is due to meet the leader of the Conservative so-called 1922 executive committee on Friday, a day after Britain goes to the polls.