The U.S. government raised grave questions over BP's safety culture Friday by imposing a record fine of $87.4 million (£53 million) on the British company for failing to fix hazards at its Texas City oil refinery in the wake of a disastrous explosion that killed 15 people four years ago.

The fine is four times higher than any previous penalty levied by America's workplace safety regulator, the Occupational Safety and Health Administration (OSHA), and it raises the possibility that a criminal prosecution of BP over the tragedy could be reopened.

In a sharply worded critique, the Obama administration's Labor Secretary, Hilda Solis, said that BP had reneged on commitments to fix flaws at America's third-biggest refinery, leaving the plant, south of Houston, Texas, in a condition that "could lead to another catastrophe".

"This administration will not tolerate disregard of our laws," said Solis, who said that BP had a moral responsibility to look after its employees at Texas City. "We don't need to see another loss of another life there. Our motto is we would like to see people go into work and be able to come home to their families."