A representative of Marie Stopes International (MSI) refused to give figures for the number of abortions carried out at its Belfast clinic, on 10 January 2013.
Tracey McNeill, vice president and director, of MSI , was briefing the Justice Committee on how the clinic was complying with the criminal law in relation to abortion in Northern Ireland.
Ms McNeill explained that the organisation wanted to protect the confidentiality of clients.
She told committee members that MSI had found a way to work with Northern Ireland's health regulators, the RQIA, and the process of application for registration was underway.
Ms McNeill said MSI's mission was "children by choice, not chance".
A number of MLAs expressed dissatisfaction with the answers given by the MSI representatives.
Patsy McGlone of the SDLP commented that they were dealing with elected representatives and "a bit more openness could be required".
The DUP's Jim Wells said nothing the MSI representatives had told the committee would help improve public confidence in its activities.
"You have been so elusive throughout the hearing," he said.
Committee chairman Paul Givan of the DUP questioned the importance of the organisation's engagement with the RQIA given that it had no role in assessing medical judgement.
Mr Givan read out part of a 2005 newspaper article in which an employee of the MSI clinic in Brixton described the operation of the clinic as "like a car production plant".
Ms McNeill said she had not worked for MSI in 2005 but "we do not run it in that way".
Pressed by Mr Givan for an assurance that MSI operated within the law she replied, "absolutely and categorically yes".