In 2015 and 2016 645 abortion pills were seized on their way to addresses in England, Wales, and Scotland, according to data obtained by the British Pregnancy Advisory Service (BPAS).
For a woman to have a termination in Great Britain they must meet certain requirements and have two doctors approve the request.
The figures suggest some women are not meeting the legal standard required for a lawful abortion so are instead buying pills on the internet.
BPAS, which wants abortion to be decriminalised, said many women were unaware they could face prosecution and lifetime imprisonment for buying pills online to induce their own abortion.
Peter D. Williams from the pro-life group Right to Life told Premier offering abortion on demand was not the answer.
"The idea that woman taking illegal abortion pills somehow justifies the total removal of right to life protections for unborn children is complete nonsense," he said.
"To suggest that the answer of unplanned pregnancy is the killing of a child is a completely wrongheaded, anti-human and inhumane response to that problem. The real answer to that problem is compassionate care to woman who are in unplanned pregnancies and help for their unborn children."
The Medicines and Healthcare products Regulatory Agency (MHRA) said the number of pills seized as part of Operation Pangea has risen from five pills in 2013 to 375 in 2016.
Sophie Walker, leader of the Women's Equality Party which supports decriminalisation, said: "Women's equality and wider choices depend on having control of our own bodies.
"In 2017, it should not be the case that women still have to fight for their reproductive rights and access to sexual health care."
