Hargreaves Lansdown has blamed low investor confidence for a six per cent decline in assets under administration last year.
The firm has also reported a 24 per cent year-on-year drop in net new business for the second half of 2018.
Chief executive officer Chris Hill says market volatility and political uncertainty kept investors conservative.
The firm’s latest results, covering the six months to 31 December 2018, show new business inflows totaled £2.5bn, a drop from £3.34bn 12 months earlier.
With the exception of a small upswing ahead of the Brexit deal vote on 15 January, the Hargreaves Investor Confidence index remains low.
Confidence in UK markets 11 months ago was similar to this month’s figure at 73 points, but the 10-year average is a far higher at 91 points.
Despite the volatility, first-half pre-tax profit for Hargreaves rose four per cent to £153.4m with new revenue increasing nine per cent year-on-year.
Hill says: “We believe it is critical that we continue to invest in opportunities for growth during difficult times if we are to capitalise on our significant long-term market opportunity.
“We are now moderating the rate of investment and remain watchful about the rate we put new costs into the business whilst market conditions remain challenging.”
Hill adds Hargreaves is still well placed in the lead-up to Brexit with up to £2.4trn revenue within the private wealth market, cash savings included.
Hill says: “Until certainty is reached, it will continue to impact markets and consumer confidence. Financial decision making becomes trickier and clients can become reluctant to invest more in volatile markets and prefer to sit on the side-lines.
“As we have done already, throughout the whole Brexit process, we will keep clients updated on our views, potential scenarios and impacts. We will also ensure that we have sufficient resources in place in order to help clients at the critical moments.”
Hargreaves had 1.1 million clients at the end of December – an increase of 45,000 since June.