LONDON — Boris Johnson, Britain’s foreign secretary, apologized on Monday for misleading remarks about a British-Iranian woman imprisoned in Iran that her family said could be used to justify, and even prolong, her sentence for sedition.

Nazanin Zaghari-Ratcliffe, a project manager for the Thomson Reuters Foundation, was arrested in Tehran last year and sentenced to five years in prison for what her family and other supporters said were fabricated allegations of plotting to overthrow the Iranian establishment.

Addressing Parliament earlier this month, Mr. Johnson condemned the imprisonment of Ms. Zaghari-Ratcliffe, saying that she had been “simply teaching people journalism” before her arrest in April 2016.

But that statement was untrue, according to her family and the foundation. They said she went to Iran on a vacation to visit family.

Mr. Johnson’s words were quickly seized upon by Iran-state television and, four days later, by the Iranian authorities, who cited them in a court hearing as proof as new evidence that she had engaged in “propaganda against the regime.”

Mr. Johnson at first equivocated, saying his remarks could have been clearer and that there was no doubt that Ms. Zaghari-Ratcliffe had been on vacation. But he failed to apologize, prompting a wave of criticism, including calls for opposition lawmakers to call for his resignation.

On Monday, Mr. Johnson addressed Parliament again, this time apologizing for the anguish he had caused the family.

“I acknowledge that the words that I used were open to being misinterpreted and I apologize to Mrs. Zaghari-Ratcliffe and her family if I have inadvertently caused them any further anguish,” he said. “The house should bear in mind that Iran’s regime, and no one else, has chosen to separate this mother from her infant daughter for reasons even they find it difficult to explain or describe.”

Mr. Johnson said that he hoped to meet Mrs. Zaghari-Ratcliffe’s husband, Richard, before traveling to Iran in a few weeks time. Mr. Ratcliffe told the BBC earlier this month that he hoped to accompany the foreign secretary on the trip to Iran so that he could see his wife for the first time in 19 months, but he was unsure if his request would be accepted.

Mr. Ratcliffe also said that he feared for his wife’s health after finding out that she had been taken to a hospital to see a specialist after finding lumps in her breasts, the BBC reported. He also said that he was concerned for her mental health and fears that she might be on the verge of “ a nervous breakdown.”