The British Chambers of Commerce, whose members employ one in five British workers, says preparations for a no-deal are being frustrated because the advice and support being offered by the government is inadequate.
The types of questions about a no-deal outcome that companies report struggling to get "visible, clear, complete, timely and actionable" information on include:
Will I be able to hire EU nationals?
Will I need to become VAT registered in every EU state?
What tariffs will I needs to pay on EU imports?
Will my shipments be held up by new customs rules?
Will my business have to pay mobile roaming charges in the EU?
What procedures will I face trading cross-border between NI and RoI?
The British Chambers of Commerce has identified 36 areas where their members are seeking clarity and have colour-coded the quality of the advice on offer.
In five cases the government’s guidance is rated "green" and therefore sufficiently detailed.
In 21 cases it is rated "amber," meaning there are gaps in the information.
In 10 cases the guidance is rated "red" indicating "little or no concrete information is available to help businesses plan".
The Director General of the BCC, Adam Marshall, says the ambiguity about how businesses should respond in a no-deal scenario could have serious consequences.
"This is vitally important to our economy, to people's jobs and to our communities," Marshall told ITV News.
"We're very close to the biggest change in trading conditions that we've experienced for a very long time and businesses are still in the dark about some of the important things they need to get ready for, in the event of no-deal."
In a statement a government spokesman said: "it is our top priority to support and provide certainty to businesses to get ready for Brexit.
"We are travelling around the UK to give businesses practical advice, have made £108m available to help them to prepare, and have been engaging with the British Chamber of Commerce and other representative groups over the past three years to make sure businesses have the information they need to ensure they are fully prepared for Brexit."
The has acknowledged that the UK is better prepared to adapt to a sudden and dramatic change in trading terms with the European Union after a no-deal Brexit than it was a year ago but all the evidence suggests businesses are still far from ready.
Take-up for the government’s "Transitional Simplified Procedures" scheme, which is designed to keep imports flowing in the event of no-deal by removing the requirement to make a customs declaration at the border, has been extremely weak.
HMRC wrote to 145,000 UK businesses months ago, asking them to consider registering. To date only 19,112 have.