The member referred there by Jacob Rees-Mogg, is Graham Brady Chairman of the 1922 committee, the body that can trigger a leadership contest within the Conservative party.
Speaking in the House of Commons, May defended the deal, arguing it would preserve the “integrity of the United Kingdom”.
Shortly after asking the PM this question, the influential MP for North East Somerset then submitted his letter to the chairman of the 1922 Committee.
He said: “Regrettably, the draft Withdrawal Agreement presented to Parliament today has turned out to be worse than anticipated and fails to meet the promises given to the nation by the Prime Minister, either on her own account or on behalf of us all in the Conservative Party manifesto.”
A no confidence vote will be triggered if Sir Graham receives 48 letters from Tory MPs.