The Irish Taoiseach made the call on Sunday, after Johnson accused the European Union of trying to “change the terms” of the Brexit divorce deal between the UK and the EU.

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“One thing I’d say to everyone is let’s not repeat some of the errors that were made in the past two-and-a-half years. Let’s not set such rigid red lines that it makes it hard to come to an agreement and let’s tone down the kind of nationalistic rhetoric,” Varadkar said to the BBC.

“As is always the case when it comes to negotiations, setting out so boldly such firm red lines actually makes coming to an agreement more difficult because the other party you are negotiating with doesn’t feel they got a fair deal unless those red lines get turned pink or bent in some way.”

Varadkar was also critical of a leaked memo urging British diplomats to sit separately from their EU counterparts at international summits — labeling it “petty” and akin to “primary school” behavior.

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UK foreign secretary Dominic Raab swiped back at the Irish leader in an interview on Sky News. “Leo Varadkar is in the midst of a, shall I say, very competitive election in Ireland. I’m not going to interfere in Irish politics and I suggest he wants to refrain from doing the same,” he said.

A series of opinion polls have forecast that Varadkar’s Fine Gael party will not be in power following next Saturday’s election.