Confidence among small firms has dropped "significantly" and is at its lowest level for three years, a new report has warned.
The Federation of Small Businesses (FSB) said the slump was most noticeable in London and the East of England, although firms in Scotland and Northern Ireland were the least confident.
Uncertainty about the strength of the UK and global economy was blamed for the fall in confidence, although pensions auto-enrolment and next month's national living wage were also causing concerns.
Sandra Dexter, FSB vice-chairman, said: "Small business confidence has clearly faltered, which is why the welcome small business focus in the Budget is so important. We need a renewed push for growth and productivity - with policy makers delivering a sustained package of support for ambitious small firms.
"The Budget included a number of important measures to help smaller businesses, particularly changes to business rates, which will see many small businesses taken out of paying rates altogether.
"Delivering on tax simplification measures will be vital - as will be pressing ahead with new investment in much-needed infrastructure. Taken together, these measures should help to boost confidence and help small firms to grow and succeed."
The report was published ahead of the FSB's national conference in Glasgow, due to be addressed by Scotland's First Minister Nicola Sturgeon, shadow chancellor John McDonnell and leader of the Scottish Conservatives Ruth Davidson.