Any Fianna Fáil TD who votes against a motion of confidence in Minister for Foreign Affairs Simon Coveney, or abstains on the vote, would face a six-month suspension from the parliamentary party, the Taoiseach has said.
However Micheál Martin said he does not think Fianna Fáil TDs will vote against the motion of confidence in Mr Coveney.
Earlier Mr Martin described Sinn Féin's decision to table a motion of no-confidence in Mr Coveney next week as "old-style naked opposition politics".
In proposing the motion, Sinn Féin said the appointment of former minister Katherine Zappone as a UN Special Envoy for Freedom of Opinion and Expression was done without a transparent process.
It said the short-lived appointment amounted to cronyism and fell below the standard expected of a government.
The motion states that Mr Coveney has not credibly explained the manner in which the appointment was handled and that the Taoiseach had failed to sanction him.
Sinn Féín TD Matt Carthy said the party had "no option" but to table the motion.
Speaking on RTÉ's Morning Ireland, Mr Martin said it was "a bit rich" of Sinn Féin and it is an "attempt to divide and conquer".
"My record as Taoiseach is that I focus on the issues of real substance that matter to the Irish people," he said.
In response to calls for him to sack Mr Coveney, the Taoiseach said he is "more than well aware" of his authority as Taoiseach and what he can and cannot do.
"Are we seriously suggesting that the appointment of a part-time envoy in itself justifies a vote of no confidence in a minister? I think that's not proportionate or balanced.
"I do not believe this is an issue that merits the removal of a minister ... I just simply do not believe that that would be a proportionate response in this case."
Mr Martin said Mr Coveney has apologised and appeared before the Oireachtas committee twice. He said that in his view, there needs to be "perspective and balance".
"I do not believe this is an issue that merits the removal of a minister, in terms of the appointment of a part-time envoy,' says Taoiseach Micheál Martin.— RTÉ News (@rtenews) September 10, 2021
He says Sinn Féin's no-confidence motion in Simon Coveney is not proportionate or balanced | https://t.co/5LRvW9OBLR pic.twitter.com/k9NfqSeeht
The Taoiseach said that lessons need to be learned from the controversy, but he expects party TDs to support Mr Coveney.
Speaking earlier on the same programme, Mr Carthy said Sinn Féin had taken the decision because the Taoiseach "refused and has failed to do his job" and hold Mr Coveney to account.
He described the actions taken by Mr Coveney as "indefensible", adding: "He has brought a narrative that is simply unbelievable and contradicted by all the available documents.
"We have heard lots of members of Fianna Fáil and other parties indicate they are not happy. Some have been front enough to accept it is an act of cronyism."
The Tánaiste has said that Sinn Féin are "throwing mud in the hope some of it sticks and in doing so they hope it will make them look better."
In a statement, Leo Varadkar said that Sinn Féin "are using their time, in the first week that the Dáil is back, not to discuss housing, the economy or the situation in Northern Ireland but rather an appointment that did not proceed.
He claimed that this "shows their warped sense of priority."
Fianna Fáil used as 'doormat' - McGuinness
There remains some angst within Fianna Fáil over the issue.
In a letter to colleagues, party TD John McGuinness said the Taoiseach had allowed Fianna Fáil to be used as a doormat throughout the controversy.
He said the party was being asked by Fine Gael to bend like a daisy in a storm and that it was time for the leader to pass on the baton.
Speaking on RTÉ's Today with Claire Byrne this morning, Mr McGuinness said he "doesn't know yet" if he will vote with the Government on the motion.
When asked if he would be willing to accept the possibility that he would be out of the party if he voted no confidence in Minister Coveney, Mr McGuinness said the question needs to be asked if that is the right action to be taking against a backbench TD.
Coveney 'put his hands up and apologised' - Humphreys
Minister for Soical Protection Heather Humpreys has attacked the move by Sinn Féin to table a motion of no cofidence in her party colleague.
Minister Humpreys said Mr Coveney had "put his hands up and apologised" for the way in which appointment of Ms Zappone was handled.
"Yes we didn't get it right. We have said that. Changes will be made," she said.
She added: "I feel that this motion of no confidence is opportunistic. When you think all the things that are happening in Northern Ireland at the minute and there is a risk to the executive I think Sinn Féin would be much better supporting Simon Coveney in the work that he has been doing there."
"Some people have short memories. It was not that long ago since Simon Coveney was part of the team that made sure there would be no hard border on this island.
"Nobody is more aware of that than I am living on the border. A good deal was got on that in terms of Brexit. It is important we focus on the real issues of the day," she added.
Opposition parties to support motion
Labour TD Aodhán Ó Ríordáin said that his party would support Sinn Féin's decision to table a motion of no-confidence.
Speaking on the same programme, he said: "The motion has been put down on confidence in the Government and we're an opposition party and we don't have confidence in the Government and we don't have confidence in how this issue has been handled."
People Before Profit - Solidarity TD Richard Boyd Barrett also said they will support the motion.
"As much as anything else, because it's such a terrible distraction from the big issues that we need to address," he said on Morning Ireland.
Aontú leader Peadar Tóibín said that how the government reacts to the fallout "could be a watershed moment for Ireland."
Speaking on RTÉ's Drivetime, Mr Tóibín said: "We could decide to reform our political system and root out cronyism in this country.
Earlier this week, Mr Coveney apologised to an Oireachtas committee over what he described as the "political fiasco" around Ms Zappone's appointment.
He has maintained that Ms Zappone did not lobby him for the job.
The minister said that he had to address the committee twice in as many weeks due to the "sloppiness" of some of his answers on the first occasion.
Additional reporting Mícheál Lehane