LONDON--Indonesian coal miner Bumi PLC (VLLRF, BUMI.LN) confirmed Monday that financier and major Bumi shareholder Nathaniel Rothschild has submitted an alternative proposal to the powerful Indonesian Bakrie family's proposal to buy out all of the U.K.-listed miner's assets for more than $1.2 billion in cash.

Mr. Rothschild, the 41 year-old scion of the Rothschild banking dynasty, submitted the offer late Friday to Bumi's board and has hired Morgan Stanley to provide financial advice on the matter, according to two people familiar with the matter.

Bumi didn't disclose any details about the proposal but said its nonexecutive board of directors would evaluate the offer with the help of the Rothschild Group, a bank which the board hired to provide an independent valuation on the proposals made to the board. The Rothschild Group isn't affiliated with Mr. Rothschild.

The miner said its board would only make a recommendation once an independent investigation into financial irregularities at Bumi's Indonesian coal assets, particularly at Indonesia's largest coal producer, PT Bumi Resources Tbk (BUMI.JK), has been completed. Bumi owns a 29% stake in PT Bumi Resources.

Mr. Rothschild's alternative proposal is likely to heighten already strained relationships between Bumi's largest shareholders and board members. The proposal seeks to remove Bumi's Chairman Tamin San and another large Indonesian shareholder, Rosan Perkasa Roeslani, from Bumi's board by offering compensation for their stakes in Bumi, according one of the people familiar with the matter.

A spokesman for Mr. Rothschild declined to comment on the matter.

Both people said Mr. Rothschild's proposal lacked details including how the transaction would be executed, financed and at what price. It also didn't mention if there were any third parties involved, according to one of the people familiar with the matter. The two however said that the proposal seemed aimed at keeping Bumi's 85% stake in PT Berau Coal Energy Tbk (BCUYF, BRAU.JK) within the London-listed miner's fold. The Bakrie Group proposed last month buying the Berau stake for $950 million once it had closed on the purchase of Bumi's 29% stake in Bumi Resources for cash and cancelling the Bakrie Group's 23.8% stake in the London-listed miner.

While Mr. Rothschild seems amenable to the part of the Bakrie proposal that would see the Bakrie family exit Bumi's board and shareholding in exchange for Bumi's stake in Bumi Resources, he opposes the entire sale of Bumi's Indonesian coal assets to the Bakrie Group, a proposal which Mr. Tan said he's willing to accept.

Mr. Rothschild resigned from Bumi's board last month, voicing concerns that Mr. Tan was determined to drive through a proposal that wasn't in the interests of Bumi's minority shareholders and seemed to favor Mr. Tan.

Analysts at Liberum Capital said, "We don't think a superior cash offer from Rothschild seems likely," adding that "any proposal surrounding Berau will relate more to a change in the share register rather than a cash offer."

-Write to Alex MacDonald at alex.macdonald@dowjones.com

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