Rio Tinto Group's (ASX:RIO) board is urging shareholders to vote against a proposal to form a committee tasked with reviewing the unification of its dual-listed structure, according to a Friday filing with the Australian bourse.

The company argued that the unification would have severe financial consequences, including significant tax costs and substantial wastage of franking credits, the filing said.

"This would ultimately harm shareholder value and could negatively affect the share price of a unified Rio Tinto," the board said.

Rio Tinto dismissed Palliser Capital's claim that a unified share price would exceed the current price of Rio Tinto, calling it flawed and unsubstantiated.

Palliser, which has pushed for the unification, also argued the dual-listing structure caused a $50 billion value loss, which Rio Tinto claims as unfounded, the filing added.

The board argued that publishing additional expert reviews would be redundant and distract from other priorities, including integrating Arcadium Lithium.

Moreover, Rio Tinto raised concerns that establishing such a committee with an external shareholder representative would undermine the board's governance role.

"The formation of a committee to review the unification of the DLC structure is against the best interests of shareholders," the board added.

In a separate filing, the company said the shareholders' vote on the dual-listing resolution requires a joint electoral procedure. This means the results of Rio's vote in London held on April 3 will be announced after the company's shareholders in Australia hold their annual general meeting on May 1.

Rio Tinto's shares fell nearly 1% in recent Friday trade.