Prime Minister Theresa May and Taoiseach Leo Varadkar haven't had any contact in six weeks despite impasses over Brexit and the re-establishment of the Assembly.
In a further sign of deteriorating Anglo-Irish relations, Mr Varadkar admitted neither side has sought to touch base since March.
"There has not been a formal phone call or meeting between the two of us in about six weeks, nor has there been a request for one in either direction," he said.
A meeting is under consideration for next week on the fringes of an EU-Balkans conference which both leaders will attend in Sofia.
In the Dail, Mr Varadkar sought to play down the significance of the gap in contact.
"Prime Minister May and I have each other's mobile phone numbers and it is possible for us to contact each other whenever we need to," he said.
"But currently the focus is on negotiations in Brussels and the various Cabinet meetings taking place in the UK to determine their position on the customs union or the customs union partnership and how that might evolve."
Fianna Fail leader Micheal Martin said he believed a "combination of chaos and disinterest in London" was to blame.
But he added: "I do not think that the Taoiseach will find a period in the last 25 years when a Taoiseach and a Prime Minister went for so long without talking, especially during such a crisis as that of the suspension of northern institutions or of Brexit."
Meanwhile, the Tanaiste and Minister for Foreign Affairs Simon Coveney attended the Future of Europe Dialogue ahead of Europe Day.
In his address, Mr Coveney pointed to the internal threats facing the EU as well as Ireland's place within the EU without Britain.
He said Europe was "facing the rise of populism, and strident political voices - both from inside and outside". Notwithstanding Brexit, Mr Coveney said while a member state of the EU has decided to leave, "others are getting ready to join".