By Sophie Borland

PUBLISHED: 00:22 GMT, 9 March 2012 | UPDATED: 03:36 GMT, 9 March 2012

An activist claims to have hacked into the website of Britain’s largest abortion clinic.

He claims to have the ‘entire database and contact details’ of women who had contacted the British Pregnancy Advisory Service and warned that information would be released today.

BPAS has been quick to reassure women who have had treatment that he would have been unable to access any medical or personal information about them, saying there is no danger their names were about to be made public.

The clinic’s website is down, so cannot be viewed. A message says it is ‘undergoing maintenance’.

Yesterday the unnamed activist wrote a message on Twitter  claiming he had ‘hacked’ into the  website of BPAS, which sees 50,000 women a year. ‘Database dump will be released tomorrow [Friday]’ he added.

Later he wrote another message under the pseudonym Pablo Escobar saying: ‘British Pregnancy Advisory Service has been attacked because they kill unborn children that have no rights. It’s murder.’

When another user of the website suggested his claims were untrue, he wrote: ‘Wrong. We have their entire database and customers’ contact details.’

Last night the chief executive of BPAS, Ann Furedi, said: ‘It’s not true that women’s details are going to be leaked. What I can say is that we are confident that women are not going to be at risk.’

The protester also put a picture on Twitter apparently showing the BPAS website after it had been hacked.

On the website’s homepage was a hacker’s logo and message which read: ‘An unborn child does not have an opinion, a choice or any rights. Who gave you the right to murder that unborn child and profit from that murder?

‘The product, abortion, is skilfully marketed and sold to women at the crisis time in her life. She buys the product, and wants to return it for a refund. But it’s too late.’

Later a spokesperson for BPAS confirmed: ‘The website of the British Pregnancy Advisory Service (bpas) was hacked into and defaced for a period on 8th March, 2012 in what appeared to be a sophisticated cyber attack by an anti-abortion extremist.

‘Around 26,000 attempts to break into our website were made over a six hour period, but the hacker was unable to access any medical or personal information regarding women who had received treatment at bpas.

‘The website does store details (names, addresses and phone numbers) of people who have requested information from bpas via the website, including those making personal inquiries as well as health and education professionals, the media and students.

‘These may have been inquiries relating to contraception, pregnancy, abortion, STI testing and sterilisation.

‘All relevant authorities have been informed and appropriate legal action taken to prevent the dissemination of any information obtained from the website.’

BPAS, which was founded in 1968, is a charity which provides abortions and counselling in 40 centres in England and Wales.

It does not receive direct funding from the Government but is paid by the NHS for some of its services, such as carrying out abortions in some hospitals and providing contraception.

The real Pablo Escobar was a Colombian drug baron, believed to have fuelled the U.S. cocaine trade during the 1980s.

The hacker’s account bore the logo of the notorious hacking group Anonymous, a collection of loosely connected online hackers from around the world.

But last night other alleged members of the group on Twitter were distancing themselves from the ‘Pablo Escobar’ tweeter, claiming he was not a member.

Anonymous is a sister group of the hacking community Lulzsec, which this week had four members arrested after an FBI sting operation.

The group’s chief, Hector Xavier Monsegur, was arrested by the FBI in June last year and worked with the agency to arrest some of the network’s most high-profile hackers.

Lulzsec members have been behind several significant online security breaches, including taking the CIA website offline and stealing from Sony’s database.