Pride of York and Pride of Bruges are being temporarily taken off the Hull-Zeebrugge route, following the collapse in passenger numbers as a result of the coronavirus lockdown.
P&O Ferries said 300 staff would be furloughed, and two other ships laid up, in addition to the 1,100 employees who were furloughed in March.
According to local reports, Pride of York has been laid up in King George Dock since April 3, while Pride of Bruges has been running a service every other day.
P&O confirmed Pride of York has been laid up and said Pride of Bruges would be laid up shortly.
Daily freight-only services are continuing between Hull and Zeebrugge via the Ro-Ro cargo ferry Norsky and the 5,000 ton lift on/lift off container ship Elisabeth.
Meanwhile on the Dover-Calais route P&O Ferries said they would run two ships, and will have laid up the other four. There is no change on the Hull to Rotterdam (Europoort) route.
The firm's ships bring in about 15 per cent of all the goods that the country uses, including large volumes of food and medical supplies.
The firm has asked the UK government for £150m of support for its operations, as well as funding from its shareholder DP World and unions, totalling £257.5m, to safeguard jobs and the viability of the business.
Janette Bell, Chief Executive Officer of P&O Ferries, said they had been waiting for government advice on the support it would give to the industry - but they'd had "nothing" so far.
She said they had to reshape the business to survive the crisis
She said: “Given the current crisis, we are having to make some tough decisions to keep the business strong.
“In March, we suspended our passenger business and furloughed 1,100 employees, to focus on maintaining the flow of freight to and from Britain.
“Like other operators, we have been waiting for the UK government’s advice on what support they can give the industry, as well as what conditions they might want to apply on things like routes and supply lines.
“However, we’ve had nothing so far and we can’t wait, as the pressure on the business continues, so we have to act."
Transport campaigner Adam Fowler said: "Despite challenges from low-cost airlines and the Channel Tunnel, P&O Ferries' operation in Hull has successfully maintained around one million passengers through the port of Hull. It is the only scheduled passenger ferry operation on the East Coast between Newcastle and Harwich."