The Financial Conduct Authority said on Thursday that Hargreave Hale Ltd, Newton Investment Management Limited and River and Mercantile Asset Management LLP (RAMAM) breached competition law.

"The infringements consisted of the sharing of strategic information, on a bilateral basis, between competing asset management firms during one initial public offering and one placing, shortly before the share prices were set," the FCA said in a statement.

"The firms disclosed and/or accepted otherwise confidential bidding intentions, in the form of the price they were willing to pay and sometimes the volume they wished to acquire."

This allowed one firm to know another's plans during the IPO or placing process when they should have been competing for shares, the watchdog said.

It fined Hargreave Hale £306,300 and RAMAM £108,600. Newton was not fined as it received immunity under the competition leniency programme, the FCA said.

"Asset management firms must take care to avoid undermining how prices are properly set for shares in both IPOs and placings. Failure to do so risks them acting illegally," said Christopher Woolard, the FCA's executive director for strategy and competition.

The FCA said it ruled there were no grounds for action in respect of conduct between Artemis Investment Management LLP and Newton that took place between April and May 2014 in relation to an IPO.

Earlier this month, the FCA fined Paul Stephany, a former fund manager at Newton, £30,000 for attempting to influence competitors during share sales. The FCA said the conduct investigated in that case related to "some of the facts" investigated under competition rules.

(Reporting by Huw Jones, editing by Kirstin Ridley and Kirsten Donovan)

By Huw Jones