Sinn Féin has dissociated itself from the endorsement by a senior republican of a blog claiming Maíria Cahill was involved in a consensual relationship with the man she says raped her.

The blog, written by an anonymous ‘republican’, makes an invective-laden attack on Ms Cahill – and questions her motives in making her accusations public.

Written under the title ‘Ruaidri Ua Conchobair’, the post on the Belfast Child blog also speculates, without any evidence, that Ms Cahill was not raped as a 16-year-old by an IRA man over 20 years her senior.

The anonymous article became a big political issue yesterday when Seamus Finucane, one of the four IRA members who Ms Cahill said interrogated her in a 'kangaroo court' about her allegations, 'liked' the blog on his Facebook page.

Mr Finucane’s endorsement was condemned by Ms Cahill as “disgusting”.

In a direct challenge to Sinn Féin deputy leader Mary Lou McDonald on Twitter, Ms Cahill wrote: “Will you condemn Finucane for doing this and apologise now?”

She also tweeted: "The IRA man who forced me to meet rapist, who Gerry Adams described as a 'decent person' saw fit to do this. Disgusting."

Last night, Ms McDonald responded on Twitter, saying the blog was “shameful” and its endorsement by anybody was wrong.

“The assertion in that blog is shameful and cruel and should not be posted anywhere by anyone.”

Fianna Fáil spokesman on justice Niall Collins said he condemned in the strongest possible terms what he described as a "deliberate online campaign" being directed as Ms Cahill as a result of her going public about her abuse.

“I am appalled by the level of abuse being directed at Maíria Cahill online. Maíria is clearly being targeted in a co-ordinated bullying campaign for having the bravery to speak out about her experiences,” he said.

Labour's Joanna Tuffy also called on Sinn Féin to dissociate itself from online attacks. "The online smear campaign being undertaken by sources associated with Sinn Fein, suggesting that 16-year-old Maíria Cahill was in some kind of consensual, lawful relationship with the man who raped her, marks a new low in this sorry debacle," she said.

“I am calling on Sinn Féin to do the right thing and to disassociate themselves from recent online attacks on Maíria Cahill that are without foundation and completely untrue.”

Northern Ireland First Minister Peter Robinson said last night Ms Cahill needed a clear personal apology from Sinn Fén. "There is a requirement for a personal apology," he said.

However, Deputy First Minister Martin McGuinness argued that the focus was on Sinn Féin when the “target has to be the alleged perpetrator of the rape”.

Separately, the Oireachtas committee on Justice has said that Ms Cahill would need to write to it in order for it to consider the possibility of a hearing.

However a senior source on the committee, chaired by Fine Gael TD David Stanton, said the Abbeylara judgement meant that the committee would have very limited powers and scope to conduct such an inquiry.

“It would be very hard for us to do anything meaningful because of Abbeylara,” said the source.