Ireland has warned countries around the world not to trust the UK because it is run by a "British government that doesn't necessarily keep its word".
Irish deputy prime minister Leo Varadkar urged countries to be careful when dealing with the UK because of the "bad faith" demonstrated in the government's plans to overhaul a key agreement signed as part of the Brexit deal.
After agreeing to the Northern Ireland Protocol - part of the Brexit arrangement that means checks on some goods and services flowing between Great Britain and NI - the UK has continually sought to change aspects of it.
The EU, and swathes of British MPs, have been unhappy about the UK's attempts to renege on the agreement, but comments by Boris Johnson's former top aide Dominic Cummings appear to have caused anger.
In a series of tweets posted late on Tuesday evening, the PM's ex chief adviser indicated that it was never the British government's intention to keep to the Brexit deal.
He said “of course” the government should be allowed to “sometimes break deals… like every other state does”.
Ireland's Mr Varadkar described the comments as "very alarming because that would indicate that this is a government, an administration, that acted in bad faith and that message needs to be heard around the world".
Demonstrating the deterioration of relations between the UK and EU following Brexit, the Tanaiste issued this warning: "At the moment they're going around the world, they're trying to negotiate new trade agreements.
"Surely the message must go out to all countries around the world that this is a British government that doesn't necessarily keep its word and doesn't necessarily honour the agreements it makes.
"And you shouldn't make any agreements with them until such time as you're confident that they keep their promises, and honour things, for example, like the protocol."
Asked if he did negotiate the deal in bad faith, Lord Frost, who signed the deal, said: "We negotiated to find a result, to get an agreement and of course, look at our actions."
Lord Frost said the government had spent "hundreds of millions" on implementing the protocol.
Will the EU and UK resolve their differences?
Ireland's deputy PM made the comments in an interview with RTE Morning Ireland ahead of the EU setting out proposals to resolve the political stand-off over trade in Northern Ireland.
It is understood the EU will offer to remove up to 50% of customs checks on British goods entering Northern Ireland and that more than half the checks on meat and plants entering Northern Ireland would be ditched, according to reports.
European Commission vice president Maros Sefcovic has promised the measures will be “very far-reaching” and address issues over the movement of such products across the Irish Sea.
While the measures may potentially go some way to reducing everyday friction on trade between Great Britain and Northern Ireland, they are unlikely to satisfy a UK Government demand over the role of the European Court of Justice (ECJ).
What is the UK asking for?On Tuesday, UK Brexit negotiator Lord Frost made clear the removal of the ECJ’s oversight function in relation to the protocol was a red line for the government.
Under the terms of the deal struck by the UK and EU in 2019, the ECJ would be the final arbitrator in any future trade dispute between the two parties on the operation of the protocol.
The UK now wants to remove that provision and replace it with an independent arbitration process.
Mr Sefcovic has insisted that the EU will not move on the ECJ issue.
He has pointed out that Northern Ireland would be unable to retain single market access – a key provision of the protocol – if the arrangement was not subject to oversight by European judges.
It is anticipated that the EU proposals, along with a wish list of reforms outlined by the government in July, will form the basis of a new round of negotiations between Brussels and London in the weeks ahead.
What's the UK's issue with the Northern Ireland Protocol?
The protocol was agreed by the UK and EU as a way to sidestep the major obstacle in the Brexit divorce talks – the Irish land border.
It achieved that by shifting regulatory and customs checks and processes to the Irish Sea.
The arrangements have created new economic barriers on goods moving from Great Britain to Northern Ireland.
This has caused disruption to many businesses in Northern Ireland and also created a major political headache for the government, as unionists are furious at what they perceive as a weakening of the Union.
However, other businesses have benefited from the terms of the protocol, which provides Northern Ireland traders unique unfettered access to sell within the UK internal market and EU single market.
One Month on the Shankill: Watch an extended eyewitness report as ITV News gained access to the Shankill Road loyalist community earlier this year following violence, as tensions rose over the Northern Ireland Brexit protocol.