Ireland has begun making contingency plans for a possible trade war between the EU and the UK in the event that Boris Johnson walks away from the Northern Ireland Brexit protocol.

Ireland’s deputy prime minister, Leo Varadkar, also confirmed that suspending the trade deal struck by Lord Frost last December was the EU’s likely response should the UK trigger article 16 of the protocol.

Her told RTE News at One on Tuesday that such a move would in effect undo the entire Brexit deal and precipitate a collapse in relations with the EU.

“I don’t think anybody wants to see the European Union suspending the trade and cooperation agreement with Britain,” he said. “But if Britain were to act in such a way that it was resigning from the protocol, resigning from the withdrawal agreement, I think the European Union would have no option other than to introduce what we call rebalancing measures to respond.”

Varadkar, who as taoiseach negotiated the protocol with Johnson during a meeting in the Wirral in October 2019, added: “I really hope that Britain doesn’t go down this road. Prime minister Johnson always spoke about wanting Brexit done.

“Brexit is kind of done, but [this] potentially undoes it and I don’t think it would be good for us, for Great Britain, and I don’t see how it would be good for Northern Ireland. And bear in mind the protocol is broadly supported by people in business and most political parties in Northern Ireland, and nobody is yet putting forward a preferable alternative to that.”

Talks between the EU and the UK over the protocol have entered their third week but sources in Brussels remain pessimistic.

Varadkar told RTE there was a cabinet sub-meeting on Brexit on Monday to “essentially dust down and restart our contingency preparations should we get into difficulty”.

The EU would have to serve notice it was suspending the trade deal so there would be no immediate barriers imposed on exporters. However, this would send alarm bells throughout business and potentially damage the UK’s relationship not only with the EU but also the US.

There are also fears that countries with significant trade links with the UK, including France, Ireland and the Benelux countries, could immediately impose 100% physical checks on lorries entering from Great Britain, causing traffic chaos on the roads in Kent.

Last December, thousands of lorry drivers were forced to spend Christmas in their cabs in Kent lorry parks and at roadsides after France demanded each driver have a negative Covid-19 test before boarding a ferry or Eurotunnel train.