A group of high-profile Conservative MPs have quit Open Britain over the pro-EU campaign's plan to unseat some of their colleagues at the general election, it emerged on Tuesday 25 April.
Former minister Anna Soubry and Nicky Morgan as well as Dominic Grieve, the chair of the influential Intelligence and Security Committee, described their support for Open Britain as "untenable" in a joint statement.
"As long-standing Conservative Party members and MPs it is untenable for us to play any further role in an organisation, such as Open Britain, which is advocating campaigning against Conservative MPs or candidates," the MPs said.
The development comes after Open Britain, The European Movement and Britain for Europe said they would direct their 600,000 supporters to support 20 pro-EU MPs and fight against 20 other "hard Brexit" MPs.
The target list included former Conservative leader Iain Duncan Smith and Oxford West and Abingdon MP Nicola Blackwood, who backed a Remain vote at the EU referendum but is a minister in Theresa May's government.
"It is understandable that during an election campaign, political differences between members of different parties become magnified," an Open Britain spokesperson said.
"Open Britain represents activists from all political persuasions who want to campaign against a hard Brexit and for a continued close relationship with Europe.
"As a grassroots organisation, we've had thousands of emails from our supporters asking how and where they should campaign during the General Election and we are trying to direct them to where they can make the biggest difference in the fight against hard Brexit.
"There is no way of getting involved in an election like this without campaigning for or against members of one party or another, so it was always going to disappoint some within a cross-party organisation.
"Our key seats list will continue to include support for those willing to campaign against hard Brexit from across the political spectrum.
"It has been a pleasure to work with some fantastic Conservative MPs in recent months and our door will always be open after the election to any that want to work with us in the future."
Asked by IBTimes UK if the Conservative MPs could return to the group after the election, a source close to Open Britain said: "Our door remains open."