During the investigation, the US watchdog found that the fund manager distributed quarterly reports and marketing materials to potential investors misstating, which exaggerated the valuation of the Oppenheimer fund’s holdings.

While working with Oppenheimer from 2005 to 2011, the manager sold global resource private equity fund to pensions, foundations, endowments, and high net worth individuals and families, using the false materials.

In October 2009, the manager modified the Oppenheimer fund’s marketing materials and increased the reported value of the fund’s largest investment Cartesian Investors-A, from $6m to nearly $9m, claiming it was "based on the underlying manager’s estimated values."

Commenting on the issue, SEC enforcement division co-director Andrew Ceresney said that the investors deserve and the law requires honest disclosure about how their investments are valued.

"Williamson improperly lured investors to the private equity fund he managed by providing false and misleading information about the fund’s performance," Ceresney added.

Earlier this year, Oppenheimer agreed to pay $2.8m in a settlement of related charges and also reimbursed an additional fine of $132,421 to settle related charges filed by the Massachusetts attorney general.

The SEC charges Williamson for violating various federal securities laws including Section 17(a) of the Securities Act of 1933, Section 10(b) of the Securities Exchange Act of 1934 and Rule 10b-5, among others.