Tánaiste and Minster for Foreign Affairs Simon Coveney has warned Cabinet colleagues that at no point in the last two-and-a-half years has the risk of a no-deal Brexit been greater.
He said that while a hard Brexit could still be avoided, Britain had failed to come up with any solutions or answers.
Mr Coveney also said that no staff working on no-deal Brexit planning should be redeployed during the summer months.
The memo brought by Mr Coveney has been drafted against the backdrop of the breakdown in talks between the Conservatives and Labour in London.
Taoiseach Leo Varadkar has said that there was detailed discussion at Cabinet today about Brexit and businesses are now going to be asked to step up their Brexit preparations.
Mr Coveney brought a memo on planning to Cabinet on a No deal Brexit.
Government ministers agreed that secondary legislation is needed in some areas and work needs to be done on EHIC (European Health Insurance Cards) and the Erasmus education programme.
The Taoiseach said that the staff are in place for Customs and Revenue and other areas where they are needed.
He said information campaigns informing businesses of the actions they need to take and the supports that are now available will be resumed.
He warned that there are businesses that are "perhaps taking the view that it is going to be alright on the night. And it may well be alright on the night but we cannot assume that.
"We will be asking businesses in particular to step up their planning and avail of the information, supports and advice and the funding that is already available."
He was responding to questions from Fianna Fáil Finance spokesperson Michael McGrath.
He asked if the Cabinet made any decision today to intensify and step up preparations and efforts to support companies and hiring extra Customs officials.
Meanwhile, British Prime Minister Theresa May will set out details of her "new deal" on Brexit in a speech at 4pm, Downing Street said.
She told a more than three hour long meeting of the Cabinet: "The Withdrawal Agreement Bill is the vehicle which gets the UK out of the EU and it is vital to find a way to get it over the line."
Her spokesman said the "new deal" includes alternative arrangements, workers' rights, environmental protections and assurances on the integrity of the UK in the event of a backstop.
It says such a conclusion poses the most immediate uncertainty to Ireland's economy.
In its latest economic outlook, the think-tank also acknowledges that while new housing completions have been "catching up with demand", there will continue to be shortages in the dwelling stock for some time.
It notes that despite having moderated recently, property prices remain high and foreign investors account for more than half of commercial property investment in Ireland.
The report, which contains analysis and projections for its 36 member countries and other major economies, says changes in the international tax regime, could affect Foreign Direct Investments by multinational firms, which would pose a significant risk for Ireland.
Economic growth, according to the OECD, is projected to remain robust, but to ease gradually to 3.9% in 2019 and 3.3% in 2020.
Additional reporting Ailbhe Conneely, Conor McMorrow, PA