The Business Secretary and former Leader of the House of Commons says John Bercow - who has the highest authority in the House of Commons and chairs MPs' debates, has failed to uphold his position and permitted a "flagrant abuse" of parliamentary process.
The Speaker has a responsibility to remain impartial and uphold parliamentary order.
It comes after MP's backed a motion to take control of the Commons timetable to pass legislation aimed at blocking a no-deal Brexit.
Writing in the Mail on Sunday Leadsom said the Speaker's role was to be "a politically impartial, independent umpire of proceedings" who was in place "to protect the constitution and oversee the behaviour of the House."
"But last week, the current Speaker failed us."
She argued that by allowing the urgent debate, a move which meant opposition and rebel MPs could pass a law blocking a no-deal Brexit, Bercow "didn't just bend the rules, he broke them" and gave "power to the Opposition".
Leadsom went on the say that the "inappropriate" use of Standing Order No24 - the rule to apply for an emergency debate - undermined governance and the vote of the British public.
"It was intended to ram through legislation for purely political reasons," she added.
In response to Bercow's actions the Conservative Party will field a candidate in his constituency of Buckingham at the next election, according to Leadsom.
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