Long-standing activist investor Brett Stone has made a last-ditch bid to scupper a proposed takeover of OnTheMarket by US firm CoStar.

CoStar – which owns US portals Homes.com and Apartments .com – has made a £100m takeover bid through its UK arm for OTM and pledges to fight for increased market share and to take on Rightmove. The offer is worth 110p per share for OTM.

The OTM shareholders make a decision this morning about whether to accept the deal.

On Friday afternoon Stone was denied his request to have the deal scrutinised by the Hearings Committee of the Takeover Panel. 

A Hearings Committee statement said: “Mr Stone stated in his original submissions that it is his public-spirited interest in the success of small business member-shareholders of OTM and in the long-term development of the United Kingdom property commerce category that has caused him to voice his opposition to the Acquisition.

“These may be very worthy considerations, but they do not mean that Mr Stone is a person affected by the Executive’s ruling, as distinct from someone taking it upon himself to speak on behalf of those he believes will be affected. Neither the ruling nor the Acquisition generally has a direct impact on Mr Stone.”

Stone – a partner at private investment partnership Edengen – last month wrote to OTM corporately as well as shareholders and independent proxy advisers, claiming the deal would be against the UK national interest and would inevitably lead to increased agency fees.

And at the end of last week he wrote an open letter to asset management company Schroders, which has given its backing to the deal. In particular he says there 110p hardly represents value to those earlier shareholders who bought into the company at 165p a share five years ago.

Stone says: “It is important that Schroders are transparent about their decision-making process in matters of national importance and set a good example as responsible custodians of companies.”

Previously Stone suggested a ‘three month go-shop’ period which would see CoStar and OnTheMarket agree to ‘a comprehensive three-month go-shop period, led by a new investment bank to solicit other proposals’. This was rejected by both OTM and CoStar.

In recent days investment proxy adviser Glass Lewis recommended that OnTheMarket shareholders vote ‘for’ the acquisition by CoStar, supporting the portal board’s unanimous recommendation. This followed a similar recommendation by another prominent independent advisor, ISS – Institutional Shareholder Services.