On BBC NI’s Talkback the Sinn Féin president, Gerry Adams, was asked whether, if elected, Sinn Féin candidates would take their seats in Westminster if they didn’t have to take, or affirm, the Parliamentary oath of allegiance. Answer, “No”. There’s a Parliamentary research paper on the history of the oath and Sinn Féin’s legal challenge in 1997 here [pdf file].
The research paper contains a quote from an Irish Times report dated 5 December 1997.
Mr Adams said the question of the oath was “a bit of a distraction”. While a change might be good for British democracy, it would not alter Sinn Fein’s position. Asked if he could see himself sitting in the Commons following a change to the oath, Mr Adams said: “No, because the issue for us is the claim of that parliament to jurisdiction in Ireland.”