UBS downgrades Adani investor GQG's stock, causing shares to plummet over 15%.

• UBS lowered its target price for GQG, the fourth biggest investor in Adani Enterprises, from AU$3.30 to AU$2.30.
• Since 2022, the Swiss firm has been covering the stock and this is the first time it has issued a downgrade.
• In January 2023, Adani's shares fell, causing GQG to invest billions in the group.

On Monday, the shares of major Adani Group investor GQG Partners dropped by as much as 15.74% after Swiss bank UBS changed its stock rating from "buy" to "neutral" on Friday.

UBS lowered its target price for GQG from AU$3.30 to AU$2.30. The stock was trading at AU$2.08 at 2:52 p.m. Sydney time.

The Swiss firm has downgraded its stock rating for the first time since it started covering GQG in 2022. The Australian-listed investment firm is the fourth largest investor in the flagship.

On Nov. 21, GQG's stock price dropped to a record low of AU$1.96 after Adani Group Chair Gautam Adani was charged with fraud in New York. The stock lost as much as 25%, marking the steepest one-day fall since its listing.

The company stated in an email to CNBC on Nov. 21 that it was monitoring the Adani situation and was "evaluating the evolving information to decide if any actions for our portfolios are necessary."

The investment firm emphasized that its portfolios are diversified, with over 90% of client assets invested in issuers unrelated to the Adani Group.

In January 2023, Adani's shares fell, prompting GQG to invest billions in the firm after a short-seller report by Hindenburg Research.

In January this year, Rajiv Jain, chairman and chief investment officer at GQG Partners, revealed to CNBC that his profits from Adani were approximately $4 billion, but he was likely to stop investing in the group.

On Friday, Adani Green Energy, the company at the center of the U.S. indictment scandal, experienced a 22% increase in its shares after a sharp decline following the indictment of its parent company.

In response to the indictment on Saturday, Adani reportedly stated, "I want to re-confirm our absolute commitment to world class regulatory compliance as we work through the legal process."

— CNBC's Anniek Bao contributed to this report.