CalSTRS, the big teachers pension fund in California, said it will vote against Kinder Morgan Inc's roughly $23 billion takeover of El Paso Corp , criticizing the deal's lack of transparency and apparent conflicts of interest.

The California State Teachers Retirement System said it would vote its approximately 2.8 million shares of El Paso stock against the merger. El Paso has about 773 million shares outstanding, according to Thomson Reuters data.

We have concerns with the lack of transparency and the apparent conflicts of interest that have surrounded the share appraisal process and we believe that shareholders may not receive full value for their shares should this transaction, as currently structured, be consummated, a CalSTRS spokesman said.

A shareholder group sued in January to stop the deal, arguing that El Paso adviser Goldman Sachs Group Inc and El Paso Chief Executive Douglas Foshee had vested interests in holding down the price for the company.

Goldman Sachs advised El Paso on the deal but also owns a sizable stake in acquirer Kinder Morgan through its private equity arm.

A Delaware judge called the negotiating process disturbing in a ruling last week, but refused to block the acquisition, saying shareholders should decide for themselves if they want to accept the deal.

El Paso delayed a planned vote on the deal after the ruling, moving the meeting at which shareholders will vote on the deal to Friday from Tuesday.

While shareholders can still change their votes before the meeting, the company said on Monday that about 70 percent of its outstanding shares had already been voted as of March 2. More than 98.5 percent of those shares were voted in favor of the deal, El Paso said.

The company needs a majority of the votes cast in order to receive shareholder approval of the sale.

The deal was worth around $21 billion at the time it was announced in October, but the value of the proposed tie-up has risen, along with Kinder Morgan's stock price, since then.

El Paso shares closed up 1.2 percent at $28.42 and Kinder Morgan closed up 2.7 percent at $36.30, both on the New York Stock Exchange on Wednesday.

(Reporting By Tim McLaughlin; Editing by Phil Berlowitz)

California