U.K. Prime Minister Boris Johnson faces the most critical week of his premiership, as he braces for the outcome of an investigation that could lead to his own colleagues ousting him.

Allegations are also mounting over the conduct of his government whips — the Conservative Party lawmakers responsible for maintaining party discipline — with Member of Parliament Nusrat Ghani claiming on Sunday that she was fired as a minister in 2020 partly because of her Muslim faith.

Several Conservative MPs and ministers rallied round Ghani, with Health Secretary Sajid Javid writing on Twitter it was a "very serious matter which needs a proper investigation.” It comes after Tory MP William Wragg accused the whips of trying to "blackmail” MPs who were challenging Johnson’s leadership by threatening to withdraw taxpayer funding from their constituencies.