The National Association of Securities Dealers, the US watchdog, has fined Piper Jaffray, the US securities and investment banking firm, $2.4m (€1.9m) for improper spinning of hot initial public offerings.

Mary Schapiro, vice-chairwoman of the NASD, said: "Spinning contributes to the public's perception that the IPO market is rigged in favour of company insiders who receive highly profitable IPO shares as a payoff for lucrative investment banking business."