Bumi Plc (>> Bumi PLC) was co-founded by financier Nat Rothschild and Indonesia's influential Bakrie family. But Bumi Plc and the Bakries have been seeking to part ways after two years of boardroom battles and a probe into financial irregularities.

Tan, Bumi's outgoing chairman, is buying the Bakries' 23.8 percent stake through Indonesia's Borneo Lumbung Energy & Metal Tbk (>> PT Borneo Lumbung Energy & Metal Tbk) in a deal which will take Borneo's stake in Bumi to 47.6 percent, it said in a statement to the Indonesia Stock Exchange on Thursday.

Bumi Plc, one of the world's largest thermal coal exporters, had on Wednesday announced a new separation plan with the Bakries which involved Tan buying the family's stake.

The second part of the latest plan involves the Bakrie family buying Bumi Plc's stake in Jakarta-listed Bumi Resources (>> PT Bumi Resources Tbk) for over $500 million in cash, a deal which Bumi said the two are discussing.

Tan's purchase of the stake is conditional upon the second part of the deal taking place plus the approval of that deal by Bumi's independent shareholders and a waiver of UK takeover rules that require an investor to make an offer for all shares in a company if its stake rises over 30 percent.

Borneo, which is struggling with its $1 billion of debt and is seeking to reduce it having breached some loan agreements that are now being renegotiated, said the deal would benefit its finances by averaging down its acquisition cost of Bumi shares.

Tan's involvement in Bumi dates from 2011 when he invested $1 billion to pull the Bakries out of a debt crunch.

"(Borneo) hopes to see, and will endeavor to restore, stability in Bumi Plc so as to allow its management to refocus on activities that create value for all stakeholders," Borneo said.

Borneo booked a $550 million net loss for its 2012 financial year, mainly due to lower commodity price and losses from its investment in Bumi Plc, according to its financial statement released on July 9.

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Rothschild, who owns a 14.8 percent stake in Bumi Plc, has criticized the latest separation plan.

The new deal differs from one originally proposed last year. In that scenario, the Bakries had agreed to exchange $278 million of cash and their shares in London-listed Bumi for the group's minority holding in Bumi Resources.

Rothschild argues the new plan enables Tan to control a company without making a takeover offer to minority shareholders and that minority shareholders should also be given the option of purchasing the Bakrie family's interest in Bumi Plc.

Bumi Plc's split from the Bakries will allow it to press ahead with a revival focused on its other subsidiary, Berau.

Bumi Plc, whose shares remain suspended after it delayed its results having found financial irregularities in a subsidiary, has become emblematic of institutional investors' worries about governance of foreign resources firms listed in London.

Rothschild, whose relationship with Bumi Plc's board and the Bakries has soured, has asked Britain's financial market watchdog to look into whether Bumi Plc has made misleading statements to the market.

British lawmakers earlier in July launched an inquiry into resources companies to examine corporate governance issues at miners, partly prompted by corruption probes at companies like Bumi Plc.

On Thursday an influential umbrella group of British investors, the Association of British Insurers, called for a rule change to protect minority shareholders.

(Reporting by Fathiya Dahrul, Sarah Young, Saeed Azhar and Fergus Jensen; Editing by Ryan Woo, Jeremy Laurence and Mark Potter)

By Sarah Young, Saeed Azhar and Fathiya Dahrul