Sinn Fein taking its Westminster seats would heighten the political temperature, according to the party leader.
British MPs rejected all of the alternative Brexit options put before them on Monday night, with one option backing the customs union losing by three votes.
Political opponents, including Ireland’s health minister Simon Harris, called on the party to drop the abstentionist policy, as they claimed Sinn Fein’s votes could have made a difference.
Mr Harris tweeted: “With a margin of only 3 votes in the House of Commons tonight, hard to see how Sinn Fein contend that taking their seats would not change the outcome on Brexit.”
Sinn Fein has held its abstentionist policy for more than 100 years, and currently has seven MPs elected to the House of Commons, but they refuse to take their seats as they say they would not swear an allegiance to a foreign power.
They are often criticised for the stance, but the party has remained consistently steadfast and party leader Mary Lou McDonald expressed exasperation that the issue is often brought up.
“Our MPs were elected explicitly on an abstentionist mandate, that position is a century old, and it’s a matter of principle,” Ms McDonald said.
“Don’t imagine for a second that seven Sinn Fein MPs could enter Westminster and make sense of the utter chaos and circus of the last number of months, that’s not a real position.
“I would suggest Sinn Feinners entering Westminster would only heighten the political temperature and, far from delivering light or clarity, I would suggest it would have the practical effect of making things more confused or chaotic.”
Earlier on Tuesday, Fianna Fail’s Thomas Byrne said that Sinn Fein voters were not married to the policy of abstentionism.
Ms McDonald noted that those who have been critical of the policy, the government party, Fine Gael and the opposition Fianna Fail, do not stand for election in Northern Ireland, which she labelled their “own abstentionist policy”.
“I would suggest that maybe, just maybe, Sinn Fein know Sinn Fein voters a bit better than Fianna Fail, who are the ultimate abstentionist party, because they don’t contest elections in the north of Ireland.
“They’re very welcome to, all politics should be all-Ireland.
“People in the north are now waiting with bated breath, and they are really concerned and worried and expect the government in Dublin to lead from the front and to protect their interests.
“This in-party squabbling is not worth a curse to people in Derry or Belfast, they’re watching now and want to see that there is a common purpose between all of us here in protecting people’s rights.
“I think we will be judged – all of us, individually and collectively – to whether or not we discharge those duties.
“You can’t convince me that parties who couldn’t even be bothered to contest elections up the road, in the north, are really bothered by what northern nationalists think, so I think we can dispense with the play acting.”