Following a ruling by a Houston appeals court, outgoing BP CEO Lord Browne will have to testify in a case conducted on behalf of 170 people who allege that they were injured by the disaster. This is despite arguments from BP lawyers that Lord Browne has no relevant knowledge to offer.

Now ExxonMobil, the world’s largest oil firm, has backed BP’s position and has asked for the ruling to be overturned. The move by BP’s major rival is seen as a preemptive strike against what could become a worrying legal precedent for the oil industry.

It is believed that plaintiff lawyers want to question Lord Browne about senior management decisions to cut back safety measures at the Texas facility. Inadequate safety procedures have already been established as a key component in the refinery explosion.

Lord Browne is due to attend court in the coming days.