Ireland will become the "meat in a dangerous sandwich" if it does not allocate extra gardaí to the border in preparation for a hard Brexit, the Dáil has heard.
Fianna Fáil justice spokesman Jim O'Callaghan has said the Government cannot rely on the word of Theresa May on a post-Brexit border and must prepare for customs posts on the island of Ireland.
Mr O'Callaghan said the Garda Representative Association (GRA) have indicated that 100 extra gardaí will be needed along the border to police it if Britain crashes out of the EU.
"Remember the border was put there, it was imposed without people on most of the island wanting it," he said.
Responding, Justice Minister Charlie Flanagan said: "It is both the firm commitment and determination of the Government to ensure that the current border arrangements continue."
He added that this is also the view of Mrs May.
Mr O'Callaghan said Fianna Fáil are also strongly in favour of retaining the current arrangement but it is "unquestionably the risk" that that may not be the case.
"It could be the case that if there is no deal between the European Union and the United Kingdom that Ireland and the island of Ireland could become meat in that dangerous sandwich.
He added that we need to be prepared for a hard border.
While he accepted the comments of the British prime minister are positive, Mr O'Callaghan said: "Her statements cannot be relied upon for the purpose of us believing that there will be no hard border.
"There is a situation within the British Government at present where they don't even know where their own negotiating policy will be with the European Union."
Mr Flanagan said a "high-level team composed of managers from across An Garda Siochana" has been set up and scoping exercises have been conducted.
"There is contingency planning within the Department of Justice, a working group of senior officials was established to manage the Department's response, to carry out a risk analysis of the UK's departure."
He said that planning has been focused on how the withdrawal agreement will work in practice.