Amber Rudd has resigned from the Cabinet and surrendered the whip she said in a statement.
The Hastings and Rye MP has quit her post as work and pensions secretary and said she was relinquishing the Tory whip after the Prime Minister sacked 21 rebels this week.
Mr Johnson removed the whip from two former chancellors and Winston Churchill's grandson after they voted to give Opposition MPs control of the order paper and start the process of blocking a no-deal Brexit.
Writing on Twitter, Rudd said: "I have resigned from Cabinet and surrendered the Conservative Whip.
"I cannot stand by as good, loyal moderate Conservatives are expelled.
"I have spoken to the PM and my Association Chairman to explain.
"I remain committed to the One Nation values that drew me into politics."
She says there is “no evidence” that Boris Johnson is seeking a deal with the EU.
The revelations were made in an interview with the Sunday Times.
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