REA, majority owned by Rupert Murdoch's News Corp, said in a statement on Monday that it sees "clear similarities" between the two groups, but has not yet approached, nor had any discussions with, Rightmove regarding any potential offer.

The Melbourne-based firm said that a combination of the two companies would provide a "significant opportunity to unlock shareholder value.

By the close of play on Friday, Rightmove's market capitalisation was valued at £4.4bn, having traded sideways since the start of the year. REA now has until the 30 September to either announce a firm intention to make an offer for Rightmove or walk away, under UK takeover rules.

REA, which like Rightmove holds a number-one position in its domestic market, also has Offices in Wanchai, Hong Kong and Gurugram, India. It is listed on the Australian Stock Exchange.

"The REA Board believes the enlarged group would represent a highly attractive investment opportunity for both REA and Rightmove shareholders, combining robust growth with strong margins and significant cash generation, enabling continued capital appreciation and shareholder returns," REA said.