Micheál Martin and Brendan Howlin have accused Leo Varadkar of putting right-wing politics ahead of the national interest in the logjam over top EU jobs.
Fianna Fáil leader Mr Martin said the Taoiseach was acting irresponsibly in joining in a right-wing bloc that effectively scuppered the appointment of Dutch politician Frans Timmermans as Commission President.
Labour leader Mr Howlin said the experienced Mr Timmermans would be good for Ireland in Brexit negotiations.
Talks between the 28 European leaders broke down this morning after a marathon 20 hour summit session ended in a stalemate.
The leaders of the EU states cannot agree on candidates for the influential posts of EU Commission President, Council President and President of the European Parliament.
The main stand-off is between the two large groupings in the EU, broadly representing the centre-right and centre-left.
Mr Varadkar represents Fine Gael in the EPP (European People’s Party) group. Their first choice, Manfred Weber, was rejected.
Mr Martin said: “I find it extraordinary that the Taoiseach is putting EPP politics before Ireland's interests when he outlines his concerns about the suggested appointment of Mr. Frans Timmermans as a compromise candidate.
“In doing so, he is aligning Ireland with the EPP parties in Poland and Hungary.
“This is particularly striking given what has been allowed to happen in these two countries in the past few months.
“Mr. Viktor Orban was actually suspended from the EPP in March because of the increasing disregard for the rule of law in Hungary, while in Poland there has been growing concern about political interference with the judiciary.
“Mr. Timmermans was not our group’s candidate, but I believe his appointment would be a fair compromise and he comes from a country that obeys and upholds the rule of law and an independent judiciary.”
Labour Party leader Brendan Howlin was also critical of the Taoiseach’s position in not supporting the socialist candidate today.
“It was disappointing and disturbing to read Leo Varadkar’s name alongside Bulgarian Prime Minister Boyko Borisov and Hungarian Prime Minister Viktor Orbán as those in the European People’s Party who have spoken out against Frans Timmermans as a future President of the European Commission.
“Borisov has faced allegations of corruption, xenophobia and threatening journalists and Viktor Orbán’s hardline, illiberal policies are well known.
“Their preferred candidate, Manfred Weber, comes from the right-wing Bavarian CSU, which is the sister party of Germany’s Christian Democrats and is more conservative than them on social and economic issues.
“The EPP has unsurprisingly failed to convince a majority in the European Parliament to back Manfred Weber as their candidate.
“It is quite normal that attention should now move to Frans Timmermans, who has a clear mandate as the Lead Candidate of the socialist group.
“He was the next highest ranked member of the previous Commission after Jean-Claude Juncker, and he is eminently qualified to lead the new broad coalition of four parties in the European Parliament, which now includes the greens and liberals alongside the conservatives and the socialists.
“Timmermans is well briefed on Ireland’s concerns in relation to Brexit and he would be a firm supporter of Ireland in the case of a disorderly UK exit, which could well happen if Boris Johnson becomes British Prime Minister.”
