Construction group Alfred McAlpine is under pressure to accept a proposed £584 million takeover approach from rival Carillion.
McAlpine, owner of the world's biggest slate quarry, rejected the 570p-a-share bid earlier this week, insisting that the proposed offer undervalued its business.
But Carillion, the UK's second-largest construction company, confirmed today that its indicative offer had won the support of two of McAlpine's major shareholders.
The company said that Schroder Investment Management and New Star Asset Management had backed its bid, with the fund manager and investment fund holding a combined stake of 14.89 per cent in McAlpine.
Carillion stressed that their support for the offer would lapse if the company does not announce its intention to make a formal offer for McAlpine by December 1st.
McAlpine said it was "disappointed" that Schroders had chosen to make a statement confirming its support for the proposed bid and stressed that it was aware its shareholder also owned a 20.1 per cent stake in Carillion.
"The board of Alfred McAlpine continues to believe that the proposal by Carillion of 570p per ordinary share materially undervalues the company," McAlpine added.
In rejecting Carillion's approach on Tuesday McAlpine said it believed its rival had undervalued its operations in light of recent "strong" results reported by the company.
The takeover target reported a 27 per cent increase in underlying pre-tax profits in interim results released in August.
McAlpine, which also stressed that it had made good progress in restructuring its business, added that it had received an earlier 560p-a-share proposed bid from Carillion on August 13th.