John Bercow, the former speaker of Britain's lower house of parliament, said on Saturday that he had joined the opposition Labour Party after spending most of his political career as a Conservative legislator.

Bercow, who clashed with Prime Ministers Boris Johnson and Theresa May over their approach to Brexit and treatment of parliament, told the Observer newspaper that he now believed the Conservative Party was "reactionary, populist, nationalistic and sometimes even xenophobic"...