Latest figures have shown the amount of money paid into investment funds last month fell to its lowest level for more than two years last month.
According to the Investment Management Association, sales of UK-based unit trusts and OEICs (open-ended investment companies) amounted to just £891 million.
The sum was reached after stripping out people cashing on on their investment or moving it elsewhere.
January's figure was the lowest since October 2008, and was also less than half of the £2 billion average invested into funds each month in the past year.
But the group cautioned that the fall in net retail sales was likely to be only a seasonal slump, as consumers invested less following Christmas.
It added that it expected sales to pick up again during March and April, as people made the most of their tax-free savings allowance either side of the new tax year.
Within the total, net ISA sales fell to £20.8 million, well down on both the £119.6 million seen in December and the £177.2 million for January 2010.
Equities continued to be the most popular asset class, accounting for 56% of total sales, with bond sales falling to their lowest level since October 2008.