Meetings of the joint ministerial committee (JMC), the forum intended to bring together the administrations in Westminster, Edinburgh, Cardiff and Belfast, are understood to be on hold because of the lack of a power-sharing executive in Northern Ireland.
Since the EU referendum, the JMC has been the main forum for the leaders of devolved administrations to raise concerns over Brexit strategy directly with Theresa May.
However, the group’s last plenary meeting was in February, despite the UK flirting with an unprecedented constitutional crisis as both the Scottish and Welsh governments threaten to withhold consent for crucial Brexit legislation.
A senior UK government insider revealed the hiatus was due to deadlocked talks between Sinn Fein and the Democratic Unionist Party.
Downing Street and the Department for Exiting the European Union said ministers and officials were consulting devolved administrations, but did not give a timetable for the next full meeting.
A Scottish Government source said the Northern Irish crisis was a “paper-thin excuse” for the delay and called for the JMC to be reconvened urgently.
Nicola Sturgeon and Welsh first minister Carwyn Jones branded the repeal bill, published on Thursday, a “naked power grab” after it confirmed EU powers in areas that are already devolved, such as the environment and agriculture, will be ring-fenced at Westminster and only released subject to negotiation.
Yesterday Mr Jones warned of an “immense constitutional crisis” if changes are not made to the European Union (Withdrawal) Bill, which will bring thousands of EU regulations into UK law.
Shadow Brexit secretary Sir Keir Starmer has also threatened that Labour could vote against the repeal bill in the House of Commons unless the government flips its position on EU powers and institutes a “presumption of devolution”.
A Scottish Government source said there was no reason a full meeting of the JMC could not go ahead, adding: “This is a paper-thin excuse from a Tory government which is paying zero respect to the devolved governments.
“If the UK government is remotely serious about its claims to want to involve all four UK nations it should agree to a reconvening of the JMC process immediately, .”
A UK government spokeswoman said: “We are committed to positive and productive engagement going forward.”