UK Work and Pensions Secretary Amber Rudd resigns from government saying she cannot stand by while loyal Conservatives are expelled, ONA reportrs citing BBC.
The work and pensions secretary said she no longer believed leaving the EU with a deal was the government's "main objective".
Ms Rudd described the sacking of 21 Tory MPs on Tuesday as an "assault on decency and democracy".
No 10 said it was "disappointed" by the resignation of a "talented" minister.
But a spokesperson added that "all ministers who joined the Cabinet signed up to leaving the EU on 31 October come what may".
A senior government source said "resignations to chase headlines won't change the fact that people want Brexit done so that government can deliver on domestic priorities".
Labour said Ms Rudd's resignation showed the government was "falling apart".
The MP for Hastings and Rye, who supported Remain in the 2016 referendum, said her resignation had been "a difficult decision".
"I will be considering my position - whether I will stand as an independent Conservative should there be an election coming up," she told the Sunday Times.