A feud between Ireland's church and state escalated on Wednesday, after the Archbishop of Dublin told Catholic priests they can resume communions and confirmations in defiance of government coronavirus guidance.

In a letter seen by AFP, Archbishop Dermot Farrell told Dublin Archdiocese priests that the ceremonies can be performed "if you consider it safe".

Government guidance currently says "it is advised" that such religious ceremonies "should not take place at this time".

The face-off between church and state has been brewing for days.

On Friday, prime minister Micheal Martin warned religious leaders against defying coronavirus curbs, which are being gradually wound down.

"I don't approve of any unilateral breaching of regulations no matter what quarter they come from," he told reporters.

He said the government's only motivation was "to protect people's health" and "that should be accepted in good faith".

But in a stinging letter - despatched on Tuesday - Farrell said current guidance is "perplexing" given the loosening of curbs on civic life and sporting events.

"Many have concluded that, in the absence of appropriate justification, these guidelines are discriminatory," the missive said.

Farrell said the four archbishops on the island of Ireland penned a letter to Martin last week, which indicated ceremonies "may resume in some parishes from mid-August".

"It is a matter of profound regret that there has been no engagement with Church representatives regarding revision of public health guidelines, he added.

Farrell said he personally favoured delaying the sacrament ceremonies until the autumn.

But "if you consider it safe to celebrate...it would be prudent to ensure that families confirm their awareness of the public health guidelines", he told priests.

Ireland is a historically Catholic nation, and although the church's grip has waned in recent decades, first holy communion and confirmation ceremonies are still treated as important rites of passage.

They are often accompanied by family parties, a particular concern in the midst of the pandemic which has killed 5,035 in the Republic.

Ireland - a nation of five million - has weathered three coronavirus lockdowns.

However vaccine uptake has been high, with nearly six million doses administered, and most major pandemic restrictions have been lifted.