BUENOS AIRES, Dec 30 (Reuters) - An Argentine judge on Tuesday ordered the state-controlled energy firm YPF to fully disclose details of its contract with Chevron Corp sought by an opposition lawmaker amid allegations of secret clauses in the agreement.
Chevron in 2013 signed a deal to explore the barely tapped Vaca Muerta shale formation, an accord that marked the largest foreign investment in Argentina's energy sector since the government seized Spanish giant Repsol's controlling stake in YPF.
Opposition legislators have said they believe the secret clauses hand concessions to Chevron that undermine national interests.
"Everything done by YPF is within the law," YPF said in a statement.
Judge Maria Jose Sarmiento gave YPF 10 working days to provide legislator Manuel Garrido details, the judiciary's internal news agency said.
YPF said it would appeal the ruling and that it met all obligations required of a company listed in Buenos Aires and New York.
Covering an area the size of Belgium, Vaca Muerta is one of the world' largest shale oil and gas formations.
Argentina passed a new law in October offering sweeteners to explorers to attract the estimated $200 billion needed to exploit the non-conventional resource.
To date, Chevron and YPF have announced joint investments totaling $2.8 billion, but that figure could reach as much as $15 billion under the terms of the accord. (Reporting by Eliana Raszewski; Editing by Richard Lough and Grant McCool)