Theresa May has vowed to fight a vote of no confidence from Conservative MPs "with everything I've got".
The ballot will be held on Wednesday evening after the threshold of letters from Tory MPs needed to trigger the contest was exceeded.
In a statement outside 10 Downing Street, the prime minister said she was ready to "finish the job" she set out on when she became leader.
And she warned ousting her would "put our country's future at risk and create uncertainty when we can least afford it" and could lead to Brexit being delayed or prevented.
Which Midlands Conservative MP's will support Theresa May?