The group behind a US-style Christian protest outside an abortion clinic in central London was urged on Thursday to stop harassing women but vowed to continue its daily vigils.

Campaigners from 40 Days for Life were "haranguing" women as they approached the building in Bedford Square in Bloomsbury, said Ann Furedi, chief executive of BPAS, which runs the clinic.

"It would be far better if they took their 'love' elsewhere and had a debate with people who wanted to have it, not women who are trying to access a lawful service," she told BBC radio.

The protest has sparked online outrage and a "40 days of choice" counter-protest amid an increase in anti-abortion activism in Britain.

A spokeswoman for BPAS, which is Britain's largest abortion provider, told AFP: "Some women find it very upsetting to be approached in this way and sometimes they say that even when they've made clear they didn't want to speak, the protesters still speak to them."

But Robert Colquhoun, a spokesman for the British arm of the US-based group, said its presence outside the clinic would continue. Campaigners are taking turns to stand outside the clinic with placards and leaflets.

"We have until April 1 for our '40 days for life' campaign," he told the BBC. "What we have is a peaceful and a prayerful vigil.

"Some people have been spoken to and we've seen wonderful transformations as a result of our campaign."

Police were called to the clinic on Monday after women complained of being filmed, but Colquhoun said the cameras were from a Christian television station and only planned to broadcast footage of the campaigners.

Protester Margaret Allain, 65, told AFP outside the clinic: "I'm here to take care of these mothers and these babies. Help is what they need, not somebody to take their child out of their womb."

BPAS said the campaign was part of a surge in protests against its service.

"We seem to have more regular protests now, larger protests. We've got a very big clinic in Brighton where there is quite an aggressive protest with very aggressive banners being displayed twice a week," its spokeswoman said.

BPAS has also been also targeted by a hacker belonging to the Anonymous group who this month admitted stealing about 10,000 database records of women who had registered with its website.

The organisation provides abortions to 55,000 women each year and also offers services such as contraception, counselling and sexual health screening.

40 Days For Life opposes abortion in any circumstances and says it has caused the closure of 23 abortion clinics. It is holding events in several countries and is urging campaigners to go to the BPAS clinic for 12 hours a day, seven days a week, for 40 days.

(Photo by @mjb via Flickr)