The Confederation of British Industry (CBI) said, optimism across the service sector fell sharply in the three months to February, while business volumes and profitability continued to fall
The CBI said business and professional services firms - such as accountants, lawyers and marketing companies - had seen the biggest fall in profits in six years over the past three months, and sentiment was weakening at the fastest rate in a decade.
Consumer-focused companies - which have benefited from rising household incomes and employment - also reported falling profits and were the most negative about the outlook for business expansion since 2009.
"Dimmed expectations for the year ahead mean it's more important than ever for the UK to avoid a no-deal scenario, which would create a perfect storm of issues," CBI chief economist Rain Newton-Smith said.
"Until politicians can agree a deal that commands a majority in Parliament and is acceptable to the UK and protects our economy, sentiment will continue to deteriorate," Newton-Smith said.