Two British twins who were still teenagers when they allegedly defrauded investors out of 1.2 million US dollars (£744,000) via a bogus "stock-picking robot" are facing charges in the United States.

US investors thought they were buying access to a stock-picking robot named Marl but the robot did not exist, according to prosecutors

The stocks selected were those of companies which paid hefty fees to Alexander and Thomas Hunter, who were aged just 16 when the alleged scheme began in 2007, said the US Securities and Exchange Commission.

As stock prices jumped, the Hunters' clients dumped their shares for a profit.

"While touting their supposed breakthrough investment technology on two websites, the Hunters were racking up fees as stock promoters through a third," said Thomas Sporkin, chief of the SEC's office of market intelligence, in a statement.

The SEC filed a civil suit against the Hunters, who are now 20, in US District Court in Manhattan.

Officials are asking the court to block the twins from the securities industry and order them to return the money they collected from investors. They are also seeking additional financial penalties.

It all began with a website called daytradingrobot.com, according to a narrative sketched out by the SEC. The Hunters drew roughly 75,000 investors, who were promised stock tips generated by a sophisticated programme.

The investors, most of them in the United States, paid for newsletters revealing the robot's insights and a "home version" of the robot software.

"The longer Marl is allowed to run on a computer ... The More Advanced He Becomes!" one of the Hunters' websites crowed, according to the SEC complaint.