EU Commissioner Phil Hogan has said it is too early to say if Ireland's unique trading relationship with the UK would be safeguarded in any future deal between Britain and the European Union.
In an interview with RTÉ News, Commissioner Hogan said it was up to all member states, including Ireland, to make their case when the negotiations with the UK get under way.
Mr Hogan said it was imperative for the UK to trigger Article 50 of the Lisbon Treaty in order to start the negotiations.
Rejecting any notion that informal talks should begin before Article 50 is triggered, Mr Hogan said: "These are issues that should have been teased out by [British Prime Minister] David Cameron in advance of calling a referendum.
"Now that he made the decision to have a referendum we have to live with the result.
"What has happened has created a huge amount of instability and uncertainty, and we need to remove that uncertainty, give clarity, and the only we can do that is to trigger Article 50 as soon as possible."
The EU agriculture commissioner acknowledged Ireland's particular difficulties.
"Ireland has a unique situation. We're the only country in the EU that has a land border with the UK.
"It's a bit early to say ... what the European Union will be prepared to give in the context of any arrangements with the Republic of Ireland."
He added: "What we need first of all is to get clarity about what are the issues at stake, get some certainty back into the system, so that the financial markets, the exporting opportunities that Ireland has with the UK - €1 billion worth of goods across the Irish Sea every day - these are the economic and financial issues that are urgent."
Mr Hogan said the EU institutions were keenly aware of the role the EU had played in the peace process.
"I am struck by the number of people in the institutions that have mentioned the north south peace process, and the fact that this has been a huge success.
"The Good Friday Agreement and all of the support from the European Union in respect of bringing peace to the island of Ireland is well understood in the European Union and all of its institutions."
However, he said that the commission had to consider the interests of all 27 member states when negotiating with the UK.
"The European Commission is in a position of being guardian of the treaty. We have to look at all of the issues for the 27 member states that are remaining, and it's up to the member state prime ministers, including the Taoiseach, to make the case - for Ireland as he is doing already."
Mr Hogan insisted that access to the European single market came with the price of accepting freedom of movement of goods, services, labour and capital.
He said it was possible that Britain could change its attitude to complying with those pre-conditions.
"These are all issues that are moving on a daily basis where people's positions are changing like sand.
"So let's see what the negotiations will bring, but we want to trigger the mechanism of the negotiations."