The FSB Small Business Index has fallen more than three points to record only the second negative reading in five years, and reach its lowest level since the months immediately following the referendum on leaving the EU in 2016.
The index score stood at -2.5 in the fourth quarter of 2017, down from +1.1 in the third quarter and significantly down from the highwater mark of +20.0 that was achieved in the first quarter of the year.
Despite the continued decline, the index has yet to match the dip to -2.9 felt in the aftermath of the Brexit vote, and small business confidence in the capital improved markedly after falling to a near six-year-low the quarter before.
Small businesses in the north of England and Scotland are particularly pessimistic.
The share of businesses expecting to downsize, close or hand on the business over the coming year stood at 14.6 per cent in the fourth quarter, up from 9.4 per cent a year ago and the largest share since data collection began in 2012.