Embattled UK Prime Minister Boris Johnson has received a new blow after Work and Pensions Secretary Amber Rudd resigned from the government and left the Conservative Party in protest at his handling of the Brexit crisis.Rudd's move late on Saturday capped a miserable week for Johnson as he tries to steer his divided country through its biggest political crisis since World War II. Her departure came just days after the prime minister's own brother, Jo Johnson, quit the government, saying he was "torn between family loyalty and the national interest."Rudd said on Saturday she could no longer endorse Johnson's approach to Brexit because he seemed determined to crash out of the European Union without a deal."The government is expending a lot of energy to prepare for 'No Deal' but I have not seen the same level of intensity go into our talks with the European Union," she wrote in her resignation letter.Johnson says he wants to take Britain out of the EU on October 31 with or without a deal with the bloc. But he lost his parliamentary majority this week and expelled 21 Conservative MPs in parliament after they supported an opposition plan to try to block a no-deal exit.Rudd, also a former interior minister who voted remain in the 2016 Brexit referendum, said the expulsion of the rebel lawmakers, who included the grandson of Britain's wartime leader Winston Churchill and two former finance ministers, was an "assault on decency and democracy.""I cannot stand by as good, loyal moderate Conservatives are expelled. I have spoken to the PM and my association chairman to explain," she wrote on Twitter.Brexit remains up in the air more than three years after Britons voted to leave the EU. Options range from a turbulent no-deal exit to abandoning the whole endeavour.In her resignation letter to Johnson, who succeeded Theresa May as prime minister in July, Rudd said: "I joined your cabinet in good faith: Accepting that 'no deal' had to be on the table, because it was the means by which we would have the best chance of achieving a new deal to leave on 31 October."However I no longer believe leaving with a deal is the government's main objective."Chaos in governmentJohnson says the only solution to the Brexit impasse is a new election, which he wants to take place on October 15, allowing him to win a new mandate with two weeks left to leave the bloc on time. He needs two-thirds of parliament's MPs to back an early election.But opposition parties said they would either vote against or abstain on calls for an election until a law to force Johnson to seek a Brexit delay is implemented."The prime minister has run out of authority in record time and his Brexit plan has been exposed as a sham," said Ian Lavery, chair of the main opposition Labour Party."No one trusts Boris Johnson. Not his cabinet, not his MPs, not even his own brother."Both Labour leaders and rebel Conservatives praised Rudd's decision to walk away from Johnson."Everyone has a point beyond which they cannot be pushed," centrist Conservative MP Nick Boles tweeted. "Amber Rudd has reached hers. How much more of the party he inherited will Johnson destroy before he has second thoughts or is stopped by his cabinet colleagues?" Labour's Brexit spokesman Keir Starmer said Johnson was "being totally found out" six weeks into his job. "Johnson government falling apart," Starmer tweeted. Brexit Party leader Nigel Farage - an anti-EU populist who is trying to forge an election alliance with Johnson - said the prime minister had made a mistake by taking Rudd on in the first place. "Why did Boris give ministerial posts to all these Remainers in the first place?" Farage asked in a tweet. "Confused thinking to say the least."