Alliance MLA Anna Lo at her Chinice Welfare office on University Street in Belfast Pic colm lenaghan

Sinn Fein has clashed with anti-abortion campaigners after the party moved to block plans to stop abortions being carried out in a private clinic.

Bernie Smyth of the pro-life campaign group Precious Life accused Sinn Fein of "betrayal" after it tabled a 'petition of concern' which will stop the progression of a controversial amendment to the Criminal Justice Bill.

Stormont's political divisions on the abortion issue will spill on to the floor of the Assembly today when the amendment seeks to ban abortions outside health service facilities.

The measure is all but bound to fail because Sinn Fein, Anna Lo of Alliance and Stephen Agnew of the Greens lodged the petition of concern, which effectively blocks it. This procedural device means the measure falls unless it is supported by a majority in both the unionist and nationalist blocks at Stormont.

Ms Smyth lambasted Sinn Fein for playing a key role in blocking the amendment and said the move would amount to "political suicide".

She added: "This will go down in history, that when an attempt was made to strengthen the laws protecting Ireland's unborn babies and close the first private abortion clinic in Ireland, it was blocked by Sinn Fein.

"Sinn Fein is now the 'Judas party'."

The last minute amendment is supported most strongly by the DUP.

That party, with 38 Assembly seats, will unanimously support it and two of its highest profile MLAs are signatories. They are Paul Givan, the chair of the justice committee, and Jim Wells, who is due to become Health Minister in succession to his party colleague Edwin Poots in June.

Other proposers include Tom Elliott of the UUP, Alban Maginness of the SDLP and Jim Allister, the TUV leader.

It is aimed at the Marie Stopes clinic which opened in Belfast last year. This private family planning clinic offers "medical abortions" up to nine weeks after conception.

Marie Stopes has stressed that it operates within Northern Ireland's strict abortion laws.

The SDLP, which has an anti-bortion position built into its constitution, is meeting this morning to consider its stance and may allow a free vote.

Some fear that the amendment is unworkable.

Ms Lo is the only Alliance member to have signed the petition. However, David Ford, the party leader, has circulated all MLAs with a letter opposing the amendment in his capacity as Justice Minister.

Despite being on the pro-life wing of Alliance, Judith Cochrane is opposing the amendment.

The UUP is also divided. Mr Elliott is amongst the proposers of the doomed measure.

But Mike Nesbitt, his successor as party leader, will vote against it. "Members have a free vote," a spokesman said.

What Mr Nesbitt has not done is support the petition of concern.

Such petitions were originally introduced to block legislation which could affect one side of the community, either unionist or nationalist, unfairly. However, legally, a petition of concern can be raised by any 30 MLAs.

In this case it is signed by all 29 Sinn Fein members plus Ms Lo and Mr Agnew.

On Monday night Mr Agnew defended the use of the petition.

"The petition of concern was designed to stop the majority of the House forcing its will on the minority," he said. "Given less than 20% of the Assembly is female, while 50% of the general population in Northern Ireland are women, my opposition is about protecting women's equality."

Belfast Telegraph