The Federation of Small Businesses (FSB) said 39% of small companies thought a no-deal Brexit would have a negative impact, compared with 34% who thought it would have no impact and 11% a positive impact. The remainder said they did not know.

Most of those firms who thought a no-deal Brexit would harm their business said they were unable to plan for this scenario.

"As the risk of a chaotic no-deal Brexit on Oct. 31 remains alive and kicking, it is worrying that many small firms have either not prepared or are finding that they can't prepare," FSB national chairman Mike Cherry said.

"Ongoing uncertainty is to blame for preparations hitting the skids with the picture still not clear as to how the UK will leave the EU on 31 October."

The average cost of small businesses' preparations for a no-deal Brexit stood at around 2,000 pounds ($2,470), rising to 3,000 pounds for companies that import and export, according to the FSB's survey of 1,062 firms conducted in late August.