More than 100 women in Northern Ireland risk imprisonment after publicly admitting they have taken abortion-inducing pills, which are illegal in the province.

The women have signed a letter openly confirming that they took abortion pills bought on the internet from pro-choice charities, further fuelling the debate prompted by the opening of the first private clinic to offer legal abortions to women in the province.

The 1861 Offences Against the Persons Act makes abortion illegal in most cases and carries a penalty of life imprisonment. Several men who have helped women obtain the pills have also signed the letter, even though the 19th-century act also makes it a serious offence to help someone procure an abortion.

The province is the only part of the UK where women cannot get an abortion through the NHS except in extreme circumstances, such as when a mother's life is at risk. As a result, thousands of Northern Irish women have crossed the Irish Sea to have terminations in English hospitals and clinics.

Pro-choice campaigners claim an attempt by assembly members Alban Maginness of the SDLP and Democratic Unionist Paul Girvan to amend Northern Ireland's criminal justice bill, to make abortions outside the NHS in the province illegal, will prevent the recently opened Marie Stopes clinic in central Belfast from providing non-surgical, early-term procedures.

In their letter the women state that they "have either taken the abortion pill or helped women to procure the abortion pill in order to cause an abortion here in Northern Ireland. We represent just a small fraction of those who have used, or helped others to use, this method because it is almost impossible to get an NHS abortion here, even when there is likely to be a legal entitlement to one."

Their letter continues: "We are publishing this letter now because of the Maginness/Girvan amendment to the criminal justice bill which we believe is aimed at closing down the debate on abortion here, as much as it is about closing down Marie Stopes. We want to emphasise that medical abortions happen in Northern Ireland on a daily basis but without any medical support or supervision. We were delighted when Marie Stopes came to Belfast as it meant that women who are unwell can access a doctor to supervise what we have done or helped others to do without medical help. And therefore have a right to a legal abortion here."

One of those who put her name to the letter, Belfast-born student Suzanne Lee, 23, told the Observer she was prepared to be arrested and taken to court over her decision last August to take abortion pills, bought on the internet from pro-choice group Women On Web, when seven weeks' pregnant. "If the pro-life people want to report me to the public prosecution service and try to send me to jail – go for it! I am willing to face the consequences because I knew doing this was illegal. I am speaking out because I'm happy to stand up in court and try to highlight how absurd this situation is," she said.

The Alliance For Choice pro-abortion group claims the Maginness-Girvan amendment, being debated at Stormont this Tuesday, will not only shut down Marie Stopes's abortion services but the entire debate.