(Bloomberg) -- Origin Energy Ltd.’s top investor rejected a revised A$19.1 billion ($12.5 billion) takeover plan by a Brookfield Asset Management Ltd.-led group, casting the year-long pursuit into new doubt.

The utility disclosed an amended bid from Brookfield and EIG Global Energy Partners and delayed a planned Thursday vote on their A$9.43 a share offer until Dec. 4, after proxy results showed the existing proposal would fail.

Under a new plan, if shareholders reject the takeover next month, the suitors intend to pursue an alternative strategy to acquire the business in separate parts at a lower price, with Brookfield offering about A$12.3 billion for Origin’s energy generation and retailing business. The group put forward an initial bid in November last year.

“This latest low-ball offer strengthens AustralianSuper’s view that the offer remains substantially below our estimate of Origin’s long-term value,” the pension fund, which confirmed it has lifted its stake to more than 17%, said in a statement. 

Origin, the country’s largest utility, should remain owned by AustralianSuper’s members and other investors, rather “than a private equity consortium planning to shortchange them,” the fund said. 

The energy company’s shares closed down 1.7% at A$8.275, the lowest price since May 25.

Under the new amendments, if the current proposed takeover went ahead Brookfield would give institutional investors an opportunity to re-invest into Origin’s energy generation and retailing business. 

In the event investors vote against the deal, Brookfield has proposed to acquire Origin’s energy unit and EIG would make an off-market takeover offer for the remaining business, which would comprise of liquefied natural gas assets. Under that scenario, investors could receive total payments of as much as A$9.30 a share, Origin said.

Origin’s board has “significant reservations as to the complexity, conditionality and differing value, and potential adverse tax outcomes to Origin and shareholders,” of the new proposals, and will assess the plans before offering a view on their merits, the target said. 

It’s possible the company makes and announces a formal decision about the new offer before the new vote in 10 days, Origin’s chairman Scott Perkins told reporters Thursday in Sydney, and cautioned that the price between the two offers was “a non-trivial difference.”

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The alternative proposal would break what the bidders see as AustralianSuper’s stranglehold on the offer, EIG Chief Executive Officer Blair Thomas said in an interview, claiming many other investors remain in favor of a transaction. “It leaves it in the hands of the majority of shareholders and it liberates them from the control of a single minority shareholder,” Thomas said.

However, the new plan’s complexity means “there is absolutely no confidence that the deal will get through,” said Jun Bei Liu, a portfolio manager at Tribeca Investment Partners. “As shareholders, at this point, we are sort of in limbo.”

Proxy ballots cast ahead of a meeting that had been scheduled for 2pm Thursday had indicated that the takeover would not receive the required 75% approval from participating shareholders, Origin said.

(A previous version of this story corrected a currency in the ninth paragraph.)

--With assistance from Amy Bainbridge and Georgina McKay.

(Updates with opposition from AustralianSuper, comments)

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