Waste management firm Shanks confirmed a 135p-a-share bid approach, but added an offer of 150p-a-share would deliver an apt value to its shareholders.

An offer of 135p-a-share, which values the firm at £535 million, was tabled by the US private equity firm Carlyle Group, though Shanks did not mention its name.

Shanks claimed that it enjoyed the support of Schroders and Legal & General in holding out for 150p that would value the firm at £595 million.

Each of the two, viz. Schroders and Legal & General owns 16 per cent stake in the firm.

Shanks’ recent statement set a benchmark for any potential rival bids.

In the after-hours trading, shares in Shanks gained 38.4p to 128½p-a-share.