The UK's biggest ports operator, AB Ports, has rejected a £2.2bn offer from a Goldman Sachs-led consortium, branding it "wholly inadequate".
Ports companies have attracted many suitors in recent months
Earlier this week the bank confirmed it was considering a possible bid with Borealis Infrastructure Management and Singapore firm GIC Special Investments.
AB Ports said the cash offer was worth 730p a share, slightly above its closing price of 717p on Wednesday.
The firm runs 21 UK sites and employs more than 3,000 people worldwide.
Speculation that it might be a takeover target began last week when the group's shares gained 10% in value.
It is thought that a rival British group, made up of investors and port operators, has been preparing its own offer for several months.
Bidders have flocked to the UK's ports groups in recent months, attracted by rising world trade volumes as well as property assets.
Dubai Ports World recently spent $6.8bn to acquire P&O, while Mersey Docks and PD Ports were taken over last year.
AB Ports handles about a quarter of the UK's seaborne traffic, with sites at locations including Hull, Grimsby, Port Talbot and Southampton.
Additionally, it has a number of businesses offering specialist services and a US division, Amports.