The Commons Speaker has refused a government request to hold a "yes" or "no" vote on its Brexit deal.
John Bercow said a motion on the deal had already been brought before MPs on Saturday, and it would be "repetitive and disorderly" to debate it again.
Saturday's sitting saw an amended motion nodded through by MPs, which withholds approval of Boris Johnson's deal until it has been passed into law.
The PM agreed on a deal with the EU last week, but it must be approved by MPs.
Speaking in the Commons, Mr Bercow said he came to the decision on the basis of a parliamentary convention dating back to 1604.
He cited Parliament's rulebook, Erskine May, which says a motion that is the same "in substance" as a previous one cannot be brought back to the Commons during the course of a single parliamentary session.
The Speaker also said the circumstances around the motion had not changed, so his ruling was "necessary to ensure the sensible use of the House's time and proper respect for the decisions that it takes".
