Three Conservative MPs have resigned, saying the party's "failure" to stand up to hardline Brexiteers has forced them to take the decision.
Sarah Wollaston, Heidi Allen and Anna Soubry have joined the new Independent Group.
In a joint letter to Prime Minister Theresa May, the MPs said: "We no longer feel we can remain in the party of a Government whose policies and priorities are so firmly in the grip of the ERG and DUP."
It comes hours after Labour MP Joan Ryan became the eighth MP from the party to resign and join the Independent Group.
The move takes the number of Independent Group MPs to 11.

Five killed in Nigeria mosque attack, police say
Helicopter crash on Tanzania's Mount Kilimanjaro kills five, aviation authority says
UK, Canada, Germany and others condemn Israel's West Bank settlement plan
Discovery of a million more potential Epstein documents delays further releases
Russia plans nuclear power plant on the moon within a decade
