Rightmove PLC announced Wednesday that it has rejected a £6.1 billion ($8.1 billion) acquisition proposal from Australian online property advertising firm REA Group Ltd., marking the third time the U.K.-based property portal has turned down an approach from Rupert Murdoch’s company.

Board Unanimously Rejects Offer

Rightmove's board dismissed the "unsolicited, non-binding, and highly conditional" offer on Tuesday, citing that it materially undervalued the company and its long-term growth prospects. After consultation with financial advisers, the board concluded that REA Group’s proposal remained unattractive, despite being the highest of three offers made in recent weeks.

Rightmove Rejects £6.1B Offer : REA Group’s Frustration

REA Group, which is majority-owned by Murdoch's News Corp., expressed its disappointment with Rightmove's rejection. "REA is frustrated by the lack of substantive engagement with Rightmove," the Australian firm said in a statement, urging Rightmove's shareholders to pressure the board to engage in discussions before the September 30 deadline.

Rightmove Rejects £6.1B Offer : Terms of the Offer

REA Group's latest offer, made Monday, valued Rightmove at 770 pence per share, a 39% premium over the U.K. company’s closing share price on August 30. The proposal included 341 pence in cash and 0.0422 new REA shares for each Rightmove share. If successful, Rightmove shareholders would own around 20% of the combined company.

Previous offers from REA Group, made earlier in September, valued Rightmove at 705 pence and 749 pence per share but were also rejected.

Potential for a Hostile Bid

REA Group CEO Owen Wilson expressed disappointment at Rightmove’s lack of engagement, hinting that the deal might move toward a hostile takeover. Russ Mould, investment director at AJ Bell, suggested that REA might bypass Rightmove’s board and appeal directly to shareholders.

"This could set the stage for a hostile approach, where REA negotiates directly with shareholders instead of the board," Mould said, noting that major asset managers, who are Rightmove's largest investors, may eventually sell if the price is right.

Next Steps

REA Group has until September 30 to make a formal offer or withdraw its bid. The Australian company reiterated that it still considers its offer "a highly compelling proposition" and remains ready to engage with Rightmove’s board.