It is believed a no-deal Brexit could cost the average Irish household between €900 and €1,400 a year.
It comes as a key European Council summit, billed as "the moment of truth" in the negotiations, sees the leaders of the EU member states hear from Theresa May in an address tonight.
It is being reported that the idea of extending the two-year Brexit transition by one year is being considered to provide more time to develop a temporary customs arrangement between the EU and the UK.
The transition would be extended in return for agreeing to prevent a hard border on the island of Ireland. However, significant issues, particularly the border issue, need to be resolved before a Brexit deal can be agreed.
EU Council president Donald Tusk has warned that without new "concrete proposals" from the British to break the logjam over the so-called Irish border "backstop", further progress may be impossible, increasing the prospect of a no-deal Brexit.
Professor of Economics at DCU Edgar Morgenroth said a no-deal Brexit could mean potential tariffs on the likes of cereal and milk.
Prof. Morgenroth said: "If you look carefully at your cereal boxes, you will find that a lot of it comes from the UK. We estimate that there could be a price increase of as much as 21% there.
"Again milk could be one of the more affected items, 30%. It is very much dependent on where we source staples and our groceries."