Abortion remains illegal in NI apart from in very limited circumstances
Northern Ireland women who travel to Great Britain for abortions can pay as much as £1,000 and are getting into debt, according to a charity.
Abortion remains illegal in Northern Ireland, except in limited circumstances when "serious risk" is posed to the mother's life, or her physical or mental health.
Each year, thousands of women travel to Great Britain to have the procedure, which was legalised 40 years ago.
The controversy has arisen again which some local MPs fear may be used to extend the 1967 Abortion Act to Northern Ireland.
A joint letter has been sent to every Westminster MP, signed by the leaders of the DUP, Sinn Fein, the SDLP and UUP opposing plans to extend the legislation.
DUP MP Jeffrey Donaldson said he hoped that "even pro-abortion MPs" would respect the wishes of politicians who represent 90% of people in Northern Ireland and debated the issue in the assembly last October.
"It is a very powerful message that we have four political leaders coming from very diverse political perspectives but united in their view that we do not want the 1967 act, with all its implications, imposed on Northern Ireland," he said.
"The issue of abortion should be left to the assembly. I don't think it has happened before that the four leaders have lobbied their fellow parliamentarians in this way."
Opposition to abortion is an official policy of the DUP, Sinn Fein and the SDLP - the UUP says while it is left to the conscience of the individual politician, party members "have consistently voted for pro-life interests".
The current law in Northern Ireland is a mixture of legislation and case law dating back as far as 1861.
Dr Audrey Simpson of the Family Planning Association accused the politicians of "completely ignoring the 80,000 people who have travelled to England for abortions since 1967".
"Our politicians are criminalising women, they are forcing them to leave their country to do something which is legal in another part of the UK," she said.
Almost 1,300 Northern Ireland women travelled to Great Britain for abortions in 2006, according to the charity Marie Stopes International whose clinics saw about half of them.
Spokeswoman Julie Douglas said the cost of travel and the procedure meant some vulnerable women were getting into debt.
"With the cost of flights and the procedure, you're talking up to £1,000 - this can be higher as time goes on because the procedure is more expensive after 14 weeks of pregnancy but it still takes time to save up.
"We try to do same-day visits where the woman can take an early flight and travel home later."
She said the availability of abortions on the NHS in Great Britain has seen a reduction in private consultations from about 100,000 ten years ago to 25,000 last year.