The Heineken Champions Cup and Challenge Cups have been suspended temporarily, the European Professional Club Rugby has announced.
It follows a directive from the French government regarding the participation of the country's clubs in both competitions amid the Covid-19 pandemic.
Irish provinces Leinster, Munster, Ulster and Connacht have been involved in the pool stages of this season's Champions Cup.
In a statement, the EPCR confirmed: "Following a directive from the French authorities that the participation of Top 14 clubs in the Heineken Champions Cup and Challenge Cup at the current time constitutes too great a public health risk, EPCR has no choice but to announce today that the 2020/21 tournaments are temporarily suspended.
"EPCR and the Ligue Nationale de Rugby took part in a meeting by audio conference last week with representatives of the French ministries of the Interior, Health and Sport, as well as of the President's office.
"Notable updates to EPCR's Covid-19 protocols were presented to the French authorities, including the addition of PCR tests no earlier than three days before matches in the tournaments, conforming to French government guidelines and supplementing the existing, meticulous contact tracing measures put in place with a view to limiting the risk of transmission.
"Against the backdrop of the recent detection of a new strain of coronavirus, the French government has directed that French clubs postpone their participation in EPCR’s tournaments for the month of January, both for matches scheduled in France and for those due to be played in the United Kingdom and Ireland.
"On the basis of this directive, EPCR had no choice but to temporarily suspend the pool stage of the Heineken Champions Cup and the preliminary stage of the Challenge Cup."
The EPCR added that they "remain committed" to resuming the competitions "as soon as practicable".
Speaking to RTÉ Sport prior to confirmation of the suspension of the Champions Cup and Challenge Cup, Bernard Jackman, who was head coach at Grenoble for six years, said that there is potential for the competitions to resume after the Six Nations which is due to start in February.
"To make up some time, they may get rid of the quarter-finals of the Champions and Challenge Cups, which were home and away, and go straight into semi-finals," he said.
"That may be a way of keeping the competition alive."
In the wake of EPCR's statement, Premiership Rugby announced a fortnight’s mid-season break.
Chief executive Darren Childs said: "The welfare of everyone involved in Premiership Rugby is crucial to us and this break in the season gives us the chance to hand some much-needed rest to our hard-working players, management, staff and match officials.