Boris Johnson is facing impeachment proceedings under proposals being considered by opposition parties in the wake of last week’s Supreme Court ruling.Plans to impeach the prime minister were put forward at a meeting of the parties on Thursday and are among options being explored to censure Johnson for the unlawful suspension of parliament.The motion, which has been drafted by Plaid Cymru, could be tabled as early as this week, disrupting Johnson’s first Conservative Party conference as leader.The development comes days after the US Democratic Party began a formal impeachment inquiry into Donald Trump over allegations that the American president pressured a foreign power to damage a political rival, raising the prospect that leaders on either side of the Atlantic could be removed from power.The process would mean the House of Commons voting on an impeachment motion, which, if passed, could lead to prosecution and trial. Historically, trials have taken place in Westminster Hall on the parliamentary estate.Though impeachment was once a common sanction against abuse of power by the executive, the last attempt to persuade the Commons to use it was in 1848, when it was alleged that Lord Palmerston, while foreign minister, had entered into a secret treaty with Russia.