The fourth proposal, made public Friday, was worth £6.2 billion (US$8.3 billion), up from the previous non-binding offer of £6.1 billion — and comes before a 1600 GMT deadline Monday for REA to table a formal bid or walk away under UK takeover rules.

Rightmove said in a statement to the London Stock Exchange that the new offer “remains unattractive and continues to materially undervalue” the company and its prospects.

In a direct message to REA, Rightmove’s chair Andrew Fisher added: “I urge them to submit a best and final proposal ahead of today’s… deadline such that we can bring certainty to this process.”

REA first made public its interest on September 2.

The initial takeover proposal was priced at £5.6 billion. There was no official figure given for the second bid.

Sector watchers have said that REA — which runs property-listing websites in Australia, Asia and North America — could be attracted by the prospect of more interest-rate cuts in Britain that would lower mortgage costs for buyers.

Analysts added that plans launched by Britain’s new Labour government for mass house building should provide a further boost to Rightmove, which also lists properties for rent.

“We respect REA and the success they have achieved in their domestic market,” Fisher said Monday.

“However, we remain confident in the standalone future of Rightmove…., the leading operator in the UK for over 20 years,” he added.

REA has stated that should it succeed in buying Rightmove, it would apply for a secondary stock market listing in London — an addition to its current trading on the Australian Securities Exchange.

The takeover attempt comes as Murdoch, 93, finds himself in the eye of a legal storm as several of his children seek to block him changing the terms of a family trust to ensure his favoured son Lachlan gains control of his sprawling media assets after his death.