ExxonMobil has thrown its weight behind rival BP in an attempt to block a precedent-setting court order requiring Lord Browne, the UK oil group's beleaguered chief executive, to testify on Friday in a civil lawsuit.

Exxon, the world's biggest public oil company, and a string of Texas business groups, are petitioning the Texas Supreme Court to overrule a decision by lower courts compelling Lord Browne to testify in the lawsuit arising from BP's Texas refinery explosion.