LONDON — Britain’s foreign secretary faced accusations on Monday of having made a misleading and careless statement about a British citizen of Iranian descent imprisoned in Iran that could prolong her ordeal there.

The foreign secretary, Boris Johnson, spoke in Parliament last month about Iran’s imprisonment of the woman, Nazanin Zaghari-Ratcliffe. He described her conviction for sedition as a mockery of justice but also said she had been “simply teaching people journalism.”

Ms. Zaghari-Ratcliffe’s employer, family and local parliamentary representative said Mr. Johnson’s statement about the activities of Ms. Zaghari-Ratcliffe in Iran not only were untrue but also had created new risks for her.

Days after Mr. Johnson’s comments, Ms. Zaghari-Ratcliffe was taken to a new court hearing, where Mr. Johnson’s words were cited as evidence that she had been engaged in “propaganda against the regime.”