A US judge has ruled that Halliburton can avoid paying most of the pollution claims that resulted from the catastrophic Gulf of Mexico oil spill because it was shielded in a contract with well owner BP.

Contractor Halliburton admitted today that it skipped a crucial test on the final formulation of cement used to seal the BP oil well that blew out in the Gulf of Mexico.

BP ignored the concerns of its contractor over the cementing of the Deepwater Horizon well shortly before it ruptured, a US hearing was told.