The US Securities and Exchange Commission sued New York hedge fund Simpson Capital Management, its owner and its head trader on Wednesday, seeking $57m (£29m) in what regulators say are ill-gotten gains from improper after-hours trading in mutual funds.

The SEC alleged in a complaint filed in federal court that two Simpson hedge funds placed more than 10,000 orders to buy and sell mutual fund shares after 4pm, when US mutual funds do their once a day pricing. The regulators said this allowed Simpson, its owner Robert Simpson and John Dowling, the head trader, to profit improperly from news announced after the New York stock markets closed.