Sky News has learnt that OnTheMarket's board is expected to recommend an offer from CoStar Group, a major US player in the online real estate industry.

Banking sources said the bid was likely to be pitched at a substantial premium to OnTheMarket's closing price on Wednesday of 70.5p.

The exact price was unclear, although one of the sources suggested the companies could announce the agreed deal as early as Thursday morning.

OnTheMarket, which floated on the London Stock Exchange's junior AIM market in 2017, has experienced tough recent trading, warning in January that it had seen abnormally high levels of agents cancelling contracts with it.

One source close to the deal said the company's takeover by CoStar, which has a market capitalisation in New York of over $33bn, would give it the firepower to take on rivals Rightmove and Zoopla.

CoStar bought Homes.com, a US online property platform, in 2021, and the purchase of OnTheMarket is expected to be presented as a continuation of its strategy.

Rightmove is listed in London, while Zoopla is part of a wider property service group backed by the private equity firm Silver Lake.

Goldman Sachs is advising CoStar on the deal, while Shore Capital and Zeus, OnTheMarket's brokers, are advising it on the takeover.

A spokesman for OnTheMarket declined to comment.