People protest in front of a US court on February 25, 2013, when the court held a trial to determine BP's liability in the 2010 Deepwater Horizon oil rig explosion and spill in the Gulf of Mexico. Photo: CFP

 
A US federal judge has refused to allow investors to proceed as a group in a lawsuit accusing BP Plc of fraud by misleading them - before and after the 2010 Gulf of Mexico oil spill - about the company's ability to respond to an accident.

US District Judge Keith Ellison in Houston denied a request on Friday to certify a class action of holders of BP's American depository shares (ADSs) who were allegedly injured by the energy giant.

"Plaintiffs have failed to discharge their burden to establish that damages in this case can be measured on a class-wide basis consistent with their theories of liability," Ellison wrote.

The judge said his decision was based largely on a US Supreme Court ruling from March holding that a class action against Comcast Corp was improperly certified.

Ellison said the Supreme Court decision "has appreciably changed the landscape for class certification."

But he said he would allow the plaintiffs another chance to argue that their case should move forward as a class action, giving them 30 days to file a new motion.

Geoff Morrell, a spokesman for BP, said the ruling "confirms BP's view, as noted in our brief and at oral argument, that plaintiffs failed to establish that this case is appropriate for class treatment."

Steven Toll, a lawyer for the plaintiffs at Cohen Milstein Sellers & Toll, said the investors "definitely do intend to refile the motion to address the court's concerns about the Comcast ruling."

Friday's decision follows a February 2012 ruling dismissing claims by purchasers of ordinary BP shares on the basis of an earlier 2010 Supreme Court ruling limiting the ability of holders of foreign securities to bring cases in US courts.

The plaintiffs are led by the New York State Common Retirement Fund and four Ohio public pension funds.

They sued BP after the April 20, 2010 explosion of the Deepwater Horizon drilling rig. The investors said BP's shares dropped in value around 40 percent in the weeks after the incident.

The plaintiffs had asked Ellison to certify a class of investors who bought ADSs between November 8, 2007 and May 28, 2010. They also asked for subclass to be certified covering purchasers of ADSs from March 4, 2009 to April 20, 2010.