Britain's biggest abortion provider has been targeted by copycat hackers from around the world since a computer expert was arrested for breaking into the charity's website and stealing women's personal records.

The revelations follow an escalation in the militant tactics being adopted by anti-abortion campaigners. Last month, the British Pregnancy Advisory Service (BPAS) said it was facing "a new era" of hardline anti-abortion protests after it called police to one of its London clinics, where women were being filmed arriving and leaving.

Last week, hacker James Jeffery, 27, was jailed for two years and eight months for stealing 10,000 personal records held by BPAS. He also defaced the website with an anti-abortion message. Since his arrest on 9 March, there have been 2,500 attempts to hack into BPAS's systems, with around a third traced to computers in North America and a third to Russia.

BPAS said the hacking was "low-level", stressing that the medical records of women were never at risk. Jeffery targeted BPAS because he disagreed with the decisions of two women he knew to terminate their pregnancies.