Updated

One of Britain's main abortion providers said Wednesday that a campaign run by a U.S.-based religious group is intimidating women who use its services.

The British Pregnancy Advisory Service said activists from the 40 Days for Life group have been holding vigils outside one of their central London clinics and had on occasion filmed people coming in and out of the building. A spokeswoman said she asked the activists to stop filming but they refused.

The spokeswoman, who requested anonymity because she said she had received hate mail, said the protests were bigger than many other anti-abortion protests.

"We've always had sporadic outbursts down the years, but I think we are seeing something, seeing protest on a scale we haven't seen before," she said.

Robert Colquhoun, a campaign director of 40 Days for Life's London campaign, said its members are carrying out a peaceful Christian prayer vigil outside BPAS's central London clinic.

The 40 Days for Life movement began in Texas in 2004, and has now spread around the world. Its members hold vigils outside abortion clinics for a 40-day period.

"It's totally unfounded to say we want to intimidate women," Colquhoun said. "We are there to pray and to show there is love in the community out there."

Colquhoun said the group did not intend to film people using the BPAS clinic but some activists did have cameras to film passers-by who were insulting them.

Britain's debate over abortion has become louder in recent years. A number of young, socially conservative lawmakers were elected to the House of Commons after the last election, including many who support more restrictive abortion laws.

Lawmaker Nadine Dorris tried unsuccessfully last year to bar abortion providers such as BPAS from counseling women about their decisions on whether to terminate their pregnancies. She wanted the counseling services to be provided by an independent body.

Dorris' campaign failed but it drew attention to providers such as BPAS and Marie Stopes International, which between them carry out around half of Britain's 200,000 annual abortions.

Last week, a man was arrested for hacking into the BPAS website and stealing sensitive data, but police did not indicate that the man is linked to those holding the vigil.

Britain's Abortion Act, first drafted in 1967, allows surgical abortions up to 24 weeks into a pregnancy. It also permits abortions after 24 weeks if doctors believe the mother's life is in danger or there is strong evidence that the fetus would be born with a severe disability. Two doctors must approve every referral to an abortion clinic.