John Bercow, Central Figure in Brexit Drama as U.K. Speaker, Switches to Labour

Mr. Bercow also was accused during his career of bullying members of his staff, claims that he denied. He stepped down in 2019.

Mr. Bercow is a strong critic of Mr. Johnson, a champion of Brexit whose rise has coincided with an exodus of pro-European Union politicians from the Conservative Party. Mr. Bercow told The Observer newspaper that the Conservatives under Mr. Johnson had become “reactionary, populist, nationalistic and sometimes even xenophobic.”

“The conclusion I have reached is that this government needs to be replaced,” he said. “The reality is that the Labour Party is the only vehicle that can achieve that objective.”

Justice Secretary Robert Buckland rejected the characterization of the party as xenophobic and said that Mr. Bercow’s decision to forgo political neutrality “actually has the effect of diminishing the force of his voice in politics.”