Boris Johnson during the launch of his campaign to become leader of the Conservative and Unionist Party and Prime Minister at the Royal Academy of Engineering in central London. Stefan Rousseau - PA Images | PA Images | Getty Images

Boris Johnson campaigned to become leader of the Conservative Party — and by default, prime minister — on a promise that he would unify his party, and indeed the entire United Kingdom, after years of fractious wrangling over the country's membership of the European Union. Instead this week his aggressive strategy on Brexit, and to some extent his personal behavior, has divided his party's lawmakers more than ever. At the start of the week, one of them defected to an opposition party in clear view of the British leader, as he stood to address the legislature's lower chamber, the House of Commons. On Wednesday night, the prime minister's office stripped 21 others of the party's parliamentary support after they voted against the government. But Johnson's approach seems also to have divided his own family. His younger brother Jo chose to resign his ministerial post and membership of Parliament on Thursday because of the "unresolvable tension" between "family loyalty and the national interest." The new prime minister's confrontational stance against Parliament has helped to unify one constituency that can obstruct him — his opponents.

The Labour party, Liberal Democrats, Scottish National Party and others joined forces to defeat Johnson's administration four times over the course of 48 hours this week, and on Friday they announced they would continue to cooperate in order to thwart his repeated demands for a snap general election on Oct. 15. The ouster of so many well-known and highly regarded members of his party on Wednesday night had proven to be particularly controversial, even for Johnson's more loyal supporters. Among the expelled figures was Philip Hammond, the recently resigned finance minister under Theresa May who had very publicly renounced that post in July, rather than serve in a Johnson Cabinet. Other victims of the surprising purge included the Conservative's longest serving lawmaker — also a former finance and interior minister — Kenneth Clarke, and a 37-year parliamentary veteran, Nicholas Soames, one of Winston Churchill's grandchildren. Several years ago Johnson, a former journalist, published a rather laudatory biography of Churchill, subtitled "How One Man Made History." But upon his elevation to prime minister, Johnson was described as a "chancer" by Soames, who acknowledged the former London mayor possessed great qualities before insisting in a BBC interview that, "they're just not the qualities that I want to see, personally, as prime minister of this country. " The fate of Soames and his expelled colleagues had been sealed after they voted alongside opposition lawmakers against Johnson to block the possibility of a no-deal Brexit on Oct. 31. The prime minister had insisted this economically damaging option should remain open to him as leverage in negotiations with his European counterparts in Brussels.

But officials at the European Commission have told member states that talks over an altered withdrawal agreement that will govern Britain's separation from the world's largest trading bloc have been slow-moving ever since Johnson took office. Johnson had repeatedly voted against May's government after she negotiated the existing deal with Brussels. Soames highlighted that fact in a valedictory speech to his parliamentary colleagues, pointing out sarcastically that Johnson's own "serial disloyalty has been an inspiration for so many of us." Soames said his vote against his own party's government represented only the third time he had rebelled in more than three decades of parliamentary service. In Parliament's upper chamber, the House of Lords, where the legislation to block an October no-deal Brexit is close to winning final approval on Friday, the mood among some Conservatives is far from positive either. "Depressed would be the description of the parliamentary party's overall frame of mind," remarked Robert Hayward, a Conservative member of the Lords, in a message to CNBC. He added that Johnson's behavior had undermined morale and been "divisive in relation to (party) unity."