Shearman & Sterling and Cleary Gottlieb Steen & Hamilton have taken leading roles in what could become the largest-ever international arbitration case – a claim against the Russian Federation that could amount to as much as $100bn (£50bn).

The claim, which is due to go before the Permanent Court of Arbitration tribunal in The Hague in November this year, relates to the bankrupt Yukos Oil Company and sees Shearman advising Yukos's majority shareholders, GML (formerly Group Menatep), with Cleary taking a role advising the Russian Federation.

It comes after Shearman's team last month found success in a related case, when a Dutch court enforced a ruling enabling GML subsidiary Moravel Investments to receive $850m (£427m) – representing the unpaid balance of a loan it made to Yukos.

The firm's team on both cases is being headed by Paris-based global head of international arbitration Emmanuel Gaillard (pictured) and also includes partners Yas Banifatemi and Philippe Pinsolle.

The firm has been working on the case since January 2005, with Shearman also representing smaller Yukos shareholders Hulley Enterprises, Yukos Universal and Vetron Petroleum in arbitrations with the Rus-sian Federation.

Cleary's team is being led by Paris-based international arbitration partner Robert Greig.

The value of the claim being arbitrated in November – which sees GML suing the Russian Federation under the Energy Charter Treaty for the assets left following Yukos's bankruptcy – is still to be finalised.

However, it is likely to have increased significantly since the original $28.3bn (£14.2bn) claim as crude oil prices have risen from around $30 (£15) per barrel then to more than $100 (£50) per barrel today, significantly increasing the value of the assets.

GML director Tim Osborne, also a tax partner with UK firm Wiggin Osborne Fullerlove, said: "The Dutch decisions show that, outside Russia, no-one believes that the forced bankruptcy of Yukos was anything other than a manipulated sham to steal the company's assets."

Holman Fenwick & Willan also gave shipping litigation advice to GML, while Olswang advised GML on UK litigation and Greenberg Traurig advised on the US aspects of the case.