The UK and EU are heading for a trade war in the row over Brexit and the Northern Ireland protocol, according to Bertie Ahern.
The former taoiseach believes the Brexit row is "probably going to get worse, not better" over the coming months.
He was speaking as Britain's Brexit minister David Frost is to set out exactly what his government wants to see changed about the deal in a speech in Lisbon this afternoon.
Further negotiations are expected in the coming weeks, with the EU expected to set out its stance tomorrow.
However, tensions between the UK and EU remain high - with Foreign Affairs Minister Simon Coveney over the weekend accusing the UK of repeatedly creating new “red line” barriers to progress.
Former Taoiseach Bertie Ahern told The Pat Kenny Show he understands Simon Coveney’s frustration with the British government’s tactics.
He said: “It’s not the way to carry on negotiations - it’s very unhelpful.
“I don’t think it’s too hard to work out what the game is… the whole game has been to try to kick the can down the road. They’ve been at it since 2016, and they’re at it again.”
One of the latest sticking points in the row has been around the role of the European Court of Justice in resolving disputes that arise, with the UK now wanting to remove the ECJ’s role.
Mr Ahern said: “[Mr Frost] knew this is the one issue the EU wouldn’t deal with.
“I think that’s just trying to muddy the waters - we shouldn’t take it too seriously.”
The former taoiseach believes the dispute is set to drag on beyond 2021, even with the upcoming fresh round of talks.
He said: “The Brexit argument, unfortunately, is probably going to get worse, not better.
“The way the negotiations line is set up now… it will go on all of November.
“If there’s a trade war issue - which is where it’s heading at the moment, either a selective one or a complete one - then 2022 will be into a trade war. That I don’t think will suit anyone, but I think that’s where Frost is pushing his luck.
"Are the British stupid enough to go into a full trade war? I think that's the question. I don't think Boris is that silly, to be honest... the EU has a lot of ways of really hurting the UK if it gets into that business."
Mr Ahern said a limited trade war would most likely see tariffs placed on particular items, rather than everything.