PD Ports has written to all its employees at Teesport
More than 100 port workers on Teesside face losing their jobs.
PD Ports has written to the 600 staff at its Teesport site warning of the risk of redundancy to about 120 posts.
It said it followed the announcement by Corus that it was set to mothball the Redcar Teesside Cast Products site after a consortium ended a contract.
PD Ports said it was forced to carry out a review as it had been handling more than two million tonnes of cast slab product annually in recent years.
In a statement it said: "PD Ports regrettably has had to undertake a prompt review of its own business needs and has today entered into consultation with employees and representatives of the 600 staff employed at PDT (PD Teesport).
"PDP has written to all PDT employees advising of the risk of redundancy of around 120 positions arising from the potential Corus TCP situation and general reduced levels of business through the port, driven mainly by the continued UK and global economic recession."
It said it had invited expressions of interest from employees over voluntary redundancy.
Fazia Hussain, regional officer of the union Unite, said the announcement had been a shock and disappointment for its members and it had concerns there would be more losses in the long run.
They are due to meet in London next week.
At the beginning of May, Corus made the announcement about the Teesside Cast Products site after a consortium, led by Italian firm Marcegaglia, pulled out of a 10-year contract to buy just under 78% of the plant's production for 10 years.
It threatens the jobs of nearly 2,000 workers.
PD Ports said that before that announcement it had seen some reductions in other cargo flows through the port and had put in place other steps to continue to reduce costs.