Business group Ibec has warned that jobs and businesses would immediately be on the line in the event of a no deal Brexit.
Ibec's Director of Policy and Public Affairs Fergal O'Brien said that adjusting to a radically new trading relationship with the UK at the end of March is not possible and not realistic.
He warned that acute trade bottlenecks would be created overnight.
"Companies are preparing insofar as they can, but the economy is simply not in a position to deal with such an unprecedented and profound shock," he stated.
Ibec said it noted the contingency plans for a no deal Brexit published by the European Commission and Government, and urged them to work collectively to bring forward more meaningful measures to support business.
It said businesses needed more information on how a no deal scenario would be managed on the ground.
A comprehensive range of state aid supports would also be required to protect jobs and businesses that are the most exposed to no deal risks, it added.
"Reckless time-wasting by the UK government is now forcing businesses to activate costly no deal contingency plans," Fergal O'Brien said.
"A comprehensive Brexit deal has been agreed and signed off by the UK Cabinet. If the UK government is unable to ratify it, it should defer or cancel Brexit," he added.
Ibec has called on the Government to establish a new enterprise stabilisation fund which would provide short-term financing support for companies affected by Brexit.
It also urges the introduction of direct capital, marketing and innovation supports for companies reorienting into new markets beyond the UK, while companies should be allowed claim VAT as an input credit, at the same time as declaring their liability, to minimise cash flow needs.
New trade support measures, including further export trade financing and export credit guarantees, should also be introduced.