* Lawyer says Doe Run Peru has 30 days to revise plan
* Workers, government ultimately want smelter to reopen (Adds quotes from government, workers)
By Patricia Velez
LIMA, April 12 (Reuters) - Creditors rejected on Thursday a restructuring plan from Doe Run Peru, a unit of U.S.-based Renco Group, casting doubt on the future of the La Oroya smelter.
Doe Run Peru's board of creditors voted to start an "operational liquidation" process that could result in the smelter being operated by a new company, Doe Run Peru revising its restructuring plan to hang on to the smelter, or outright liquidation of the plant.
La Oroya, once one of the largest smelters in Peru, has been shut since 2009 because of protracted financial problems and a stalled environmental cleanup in what has been ranked as one of the 10 most polluted places in the world.
Under Doe Run Peru's "operational liquidation," the unit controlled by U.S. billionaire Ira Rennert will remain in charge of La Oroya for up to a year and is required to pay its workers.
"In principal there will be a six-month period that could be extended by another six months. The question is whether Doe Run Peru presents a plan that is acceptable to the creditors," Diego Calmet, president of the board, told reporters.
Another board member said creditors would start looking for a new company to operate La Oroya, which processed copper, lead and other metals.
A Doe Run Peru manager confirmed that the restructuring plan had been rejected, but said the company would fight to hold on to the smelter.
"We are going to find a solution so that the Doe Run Peru plan is approved," manager Juan Carlos Huyhua said.
A lawyer for Peruvian mining company Buenaventura said Doe Run Peru had 30 days to revise its restructuring plan or the board of creditors would likely choose a new operator or liquidate the plant entirely.
The Peruvian government, Doe Run Peru's main creditor, did not consider the initial restructuring plan viable. It would have relied in part on $200 million in credit from commodities trader Glencore.
Minister of Energy and Mines Jorge Merino Tafur has said the plan would have made the Peruvian state assume potential liabilities for environmental lawsuits.
The Peruvian government holds 36 percent of Doe Run Peru's debt, while Doe Run Cayman, a special unit of the Renco Group, has 35 percent. The other creditors are mostly mineral traders and suppliers. The company owes creditors at least $100 million.
Doe Run Peru inherited the La Oroya smelter from state control in 1997. It had operated with few environmental controls and had contaminated the city and surrounding area with toxic amounts of lead.
Former President Alan Garcia revoked Doe Run Peru's license to operate in July 2010 after it failed to meet an environmental cleanup deadline, but said the future of the company was in the hands of a board of creditors.
In January, creditors voted not to outright liquidate Doe Run Peru, which was once the sixth largest metals exporter in the country.
While the government opposed Doe Run Peru's restructuring plan, President Ollanta Humala, who took office in July, has said he favors reopening the La Oroya smelter. It provides jobs for some 3,500 workers.
"No workers will be fired because this process allows the company to keep operating as a business unit," the Ministry of Energy and Mines said in a communique on Thursday.
Mining workers, however, condemned the government for opposing the restructuring plan, which if approved would have led the way to resumed operations at La Oroya.
"We have been betrayed by the ministry of energy and mines," said Luis Castillo, president of the Federation of Mining Workers of Peru. (Reporting By Patricia Velez; Writing by Caroline Stauffer)