LONDON — Prime Minister Theresa May has delayed so many decisions on Britain’s withdrawal from the European Union that critics accuse her of turning can-kicking into a political art form.

On Tuesday she did it again, this time with just 45 days to go before Britain plans to leave the bloc.

Undeterred by the looming deadline, Mrs. May pleaded with British lawmakers for more time, saying she is still in talks with officials in Brussels.

“We now all need to hold our nerve to get the changes this House requires and deliver Brexit on time,” Mrs. May said.