Ireland's foreign minister Simon Coveney said on Saturday that Britain was demonstrating "perverse nationalism" by seeking to reach a trade deal with the United States before the European Union and questioned whether it was a trustworthy partner.
"This idea that Britain can get there first is narrow minded thinking, frankly. It's a perverse nationalism when actually Britain and the EU should work together as partners," he said in an interview with The Times newspaper.
Coveney advocated Britain working with the EU and Canada to reach a joint trade deal with the United States, although the EU does not currently have plans for a major US trade deal.
He also questioned Britain's trustworthiness following its plans to unilaterally delay imposing checks required by the Brexit deal on some food products travelling from England, Scotland or Wales to Northern Ireland.
"It has reinforced an awful lot of the doubts in Brussels about whether or not this really is a British government we can rely on to be a trusted partner when it comes to implementing what has already been agreed," he said.
Prime Minister Boris Johnson views the ability to strike trade deals as one of the main benefits of Brexit and sees a deal with the United States as a big potential prize.
Relations between London and Dublin have deteriorated since Britain voted in 2016 to leave the European Union.
Trade arrangements in the British province of Northern Ireland have proved a particular sticking point.
In a separate interview with Northern Ireland's News Letter newspaper, Brandon Lewis, Britain's Northern Ireland secretary, indicated that 'grace periods' for the food checks should be extended indefinitely until a new long-term agreement was reached.
"My position and the government's position in terms of the grace period we've got for chilled meats at the moment is not that at the end of that grace period there is a cliff edge; it's that we use the grace period to get a permanent solution to ensure that those products can continue to flow," Lewis said.