There are "precious few indications" that the UK is prepared for what lies ahead after Brexit, according to EU Commissioner Phil Hogan.
"The rhetoric from Prime Minister May and most of her cabinet has unfortunately been heavy on spin and light on facts," he said, warning that the UK white paper published last month "clearly points in the direction of a hard Brexit".
The Agriculture Commissioner made his comments in a video message delivered to Ibec's business leaders conference in Dublin yesterday.
The conference was also addressed by President Michael D Higgins.
"In order to secure the least harmful outcome, the UK government needs to enter the negotiations with a more realistic approach," he added.
Mr Hogan also said that Brexit will present opportunities for Ireland, but that business leaders must "do more to pave the way".
"For example, is the need for more housing, infrastructure and schools in Dublin being escalated to the urgent priority it needs to be?" he said.
Ibec ceo Danny McCoy told the conference that it was time to put the bust behind us. "Get over it," he said. "It's 10 years ago."
He said that much more needs to be invested by the Government in infrastructure, and that a failure to do so risks creating serious long-term economic and social problems.
Mr McCoy also warned delegates that the potential implications of Brexit are "so profound that companies cannot afford to take a wait-and-see approach".
He said Irish businesses not only have to deal with the impact of weak sterling on trade flows, but also the future complexity of operating under dual regulatory frameworks and other issues such as additional supply chain complexity.