The Irish prime minister, Leo Varadkar, has raised the prospect of uniformed police or soldiers being deployed to the border with Northern Ireland in the event of a chaotic and disorderly Brexit.

In the most explicit warning yet of the consequences of a no-deal Brexit, he said in a worst-case scenario, a hard border could “involve people in uniform and it may involve the need, for example, for cameras, physical infrastructure, possibly a police presence, or an army presence to back it up”.

His remarks in a Bloomberg TV interview at the World Economic Forum in Davos on Friday appear to mark a change of approach by Varadkar, who has repeatedly vowed not to put any cameras or infrastructure on the border, which has not had checkpoints since the peace deal 21 years ago.

The warning came a day after Irish police chiefs denied they had drawn up secret plans to send 600 officers to beef up border security if Britain crashes out of the EU on 29 March without an agreement.

Hints of police or soldiers being deployed will heighten concerns in the border regions, where previously warring communities have enjoyed peaceful coexistence for the past two decades.

Referring to a car bomb in Derry a week ago, Varadkar told Bloomberg putting any personnel on the border had to be seen in the context of the history of the Troubles.

“The problem with that in the context of Irish politics and history is those things become targets – and we’ve already had a certain degree of violence in the last few weeks. I just don’t want to see that come back,” he said.

Varadkar also lashed out at Brexiters who are blaming Ireland for the backstop, when it was the solution the EU came up with to address Theresa May’s red lines on the customs union and single market.

“We’re the ones already giving,” he said. “The UK wanted a review clause in the backstop and we agreed to that, the UK wanted a UK-wide element, so why is it the country that is being victimised is the one that’s always asked to give?”

His remarks serve to highlight the parallel direction of politics in the EU, which last night repeated that it was in solidarity with Ireland over the backstop, and the UK, where May appears to be winning over opponents including the Democratic Unionist party and Brexiter MPs with promises of changes to the backstop.

Varadkar said: “This is a problem caused by Britain. We came up with a solution. Now that parliament has rejected it, shouldn’t they be offering us something? Why are we the ones who are being constantly asked to help solve the problem they have created? What are they offering us? Nothing at the moment.”

His remarks came after a phone call between the European commission president, Jean-Claude Juncker, and Varadkar in which they agreed to step up no-deal preparations.

France is also helping Ireland in the event of a no-deal Brexit, with political and commercial leaders from Normandy visiting Dublin this week to discuss contingency plans involving cargo ships travelling directly to the ports of Cherbourg, Dieppe and Ouistreham in order to bypass Britain.

Currently, the vast majority of lorries destined for France use the UK as a “landbridge” via Holyhead and Dover ports.

In the case of a no-deal Brexit, this route would be threatened as tariff and customs barriers would be erected entering and leaving the UK.

Hervé Morin, the president of Normandy, said the three ports would be enhanced with sufficient numbers of customs officials and border inspection posts for animal and food health checks in time for 29 March.

It also emerged on Friday that Seaborne Freight, the company handed a £13.8m contract to run no-deal Brexit ferries from Ramsgate despite having no ships has started advertising for staff.

Seaborne Freight is hiring a stevedore and an operations assistant, with just over 60 days to go before Brexit Day.