Allen & Overy, Australia's Mallesons Stephen Jaques and New Zealand's Simpson Grierson are advising UK energy giant BG Group on its $13bn (£6.5bn) hostile takeover bid for Origin Energy, Australia's second-largest energy company.

Clayton Utz is representing Origin, which has advised its shareholders to take no action on the bid.

The $13bn offer is BG's third bid for Origin and comes after Origin rejected an identical offer at the last minute in May. Origin said in May it believed the company was worth more than $13bn, especially in light of the $2.6bn (£1.3bn) merger between Malaysia's state oil company Petronas and Australian gas company Santos.

BG's chief executive, Frank Chapman, said that the Petronas transaction was "not relevant" to his company's offer for Origin and that $13bn was likely to be as high as BG would go.

The offer amounts to $15.50 (£7.77) for each share of Origin stock. BG's initial offer, placed in April, valued Origin at about $14.70 (£7.38) per share. At that time, Origin's stock was trading at just over $10 (£5.02) per share, but the price has jumped to more than $16.40 (£8.23) as investors predict that Origin will receive a better takeover offer.

This article was first published in The American Lawyer, Legal Week's US sister publication.