The Sunday Times said, citing a senior Tory, that Crosby was masterminding a nationwide campaign against May's Chequers plan, as he believed the prime minister's proposal would betray Brexit voters and eventually harm the Conservative Party at the next elections. Crosby's staff was reportedly in contact with the European Research Group, a prominent lobby for a hard Brexit.
The outlet suggested that the plot envisioned Johnson in Downing Street, as "there was no way [May] would survive" if her Brexit plan was ruined.
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The cabinet's decision to relax Brexit conditions resulted in resignations of Johnson and Brexit Secretary David Davis in protest against the government's stance.
The United Kingdom is expected to leave the European Union in March 2019, but the negotiations are still in course, as the terms of Brexit are unclear.