“After the July 7 attacks, this is not the time to be antagonizing Britain by presenting Muslims as something sinister,” said Imran Ahmad, the author of “Unimagined,” an autobiography about growing up Muslim in Britain, and the leader of British Muslims for Secular Democracy. “The veil is so steeped in subjugation, I find it so offensive someone would want to create such barriers. It’s retrograde.”

Image Faatema Mayata, a 24-year-old teacher, said her veil was linked to her identity as a Muslim. Credit... Hazel Thompson for The New York Times

Since South Asians started coming to Britain in large numbers in the 1960s, a small group of usually older, undereducated women have worn the niqab. It was most often seen as a sign of subjugation.

Many more Muslim women wear the head scarf, called the hijab, covering all or some of their hair. Unlike in France, Turkey and Tunisia, where students in state schools and civil servants are banned from covering their hair, in Britain, Muslim women can wear the head scarf, and indeed the niqab, almost anywhere, for now.

But that tolerance is slowly eroding. Even some who wear the niqab, like Faatema Mayata, a 24-year-old psychology and religious studies teacher, agreed there were limits.

“How can you teach when you are covering your face?” she said, sitting with a cup of tea in her living room in Blackburn, a northern English town, her niqab tucked away because she was within the confines of her home.

She has worn the niqab since she was 12, when she was sent by her parents to an all-girl boarding school. The niqab was not, as many Britons seemed to think, a sign of extremism, she said.

She condemned Britain’s involvement in Iraq, and she described the departure of Mr. Blair at the end of this month as “good riddance of bad rubbish.” But, she added, “there are many Muslims like this sitting at home having tea, and not taking any interest in jihad.”