Rightmove has rejected a third bid of £6.1bn for the property portal from an Australian rival owned by Rupert Murdoch.

Earlier this week, Rightmove said it would consider the new proposal from REA Group, but its board said in a market statement this morning it had unanimously rejected the offer because it “materially undervalues the company and its future prospects”.

Richmond-based REA, which is held by News Corp, said it was “disappointed” by the rebuff and is “frustrated” because it has had “no substantive engagement with Rightmove’s board”.

REA adds that its offer remains “a highly compelling proposition” and urges Rightmove’s shareholders to encourage its board “to engage in constructive discussions with REA to work towards a recommended transaction”.

REA has offered the Rightmove board a bid worth 761p for the firm’s shares, valuing the business at £6.1bn.

REA says this is a 9.2% increase on its second bid for Rightmove on 5 September and a 39% premium on the UK firm’s undisturbed share price on 30 August, the day before the Australian firm’s interest became public.

Rightmove shareholders would hold around 20% of the enlarged business.

REA employs almost 3,000 staff trades across Australia, Asia and the US under several brands, including PropTrack, realator.com and PropTiger.com.

Rightmove’s board has urged its shareholders to “take no action in respect of the increased proposal”.

Shares in Rightmove edged 0.2% higher to 684.2p in morning trading.