Newton has sacked an employee following a Financial Conduct Authority investigation into possible competition breaches.
Last week the FCA said it was investigating four fund houses over concerns they may have broken competition law.
In a statement, Newton said: "We are not able to comment on individuals, but we can confirm that we have taken disciplinary action as a result of the activity.
"One employee was suspended at the time; this individual has since been subject to disciplinary action and dismissed."
The company has not identified the individual involved.
Last week the FCA issued a "statement of objections" to Artemis Investment Management, Hargreave Hale, Newton Investment Management and River & Mercantile Asset Management.
This gives the firms notice the FCA thinks they have infringed competition law and the opportunity to respond to this claim, but does not mean any law has been broken and may not lead to an infringement decision.
The FCA alleged the four firms shared information by disclosing the price they intended to pay, or accepting such information, or both, in relation to one or more of two initial public offerings and one placing, shortly before the share prices were set.
Among the allegations was the claim that in 2014 Artemis and Newton shared information about the price they intended or were willing to pay for shares in relation to another IPO.
Newton has said it is cooperating with the regulator and that the investigation surrounds a "very small number" of its UK equity-focused strategies and has added that clients or investors have not suffered a loss as a result of this activity.