Around 200 protesters gathered outside the ferry terminal compound in Hull before marching onto the site and banging on the doors of the terminal building.
The marchers, including a number of sacked workers, walked past the tied-up Pride of Hull ferry but got no response from anyone inside the P&O building.
Outside the gates, the rally was addressed by union officials as well as former Labour leader Ed Miliband and Labour’s Hull East MP Karl Turner.
More than 200 protesters gathered outside the Port of Liverpool.
Metro mayor of Liverpool Steve Rotheram, Greater Manchester mayor Andy Burnham and Sefton Central MP Bill Esterson joined the demonstration.
Labour MP Mr Esterson said: “I think we’ve got amazing solidarity from trade unions across the north of England and local people.
“Like everyone, I’m outraged at the appalling abuse of ordinary people by DP World.”
Protesters held flags and signs, including one which said: “Shame on you!! P&O stop the carve up.”
Lorry drivers on their way to and from the port beeped their horns in support.
Speaking at the protest at the Port of Liverpool, Greater Manchester Mayor Andy Burnham said the Government should consider nationalising P&O.
He said: “I say to the Prime Minister: you have to step in and you have to deliver on your commitment to strengthen employment law so this kind of gangster practice can’t be allowed to happen any more.”
The shadow transport secretary has said that 800 P&O workers losing their jobs is “nothing short of a national scandal”.
Louise Haigh, who joined protesters in Dover, told the PA news agency: “It’s nothing short of a national scandal that 800 P&O workers were unceremoniously dismissed on a pre-recorded Zoom call yesterday and I wanted to come straight down to Dover to stand with these workers and show my full solidarity.”
She added: “I will be taking action in Parliament next week to push the Government to take sanctions against P&O now, to push leverage on them, to force them to change course and if it’s not illegal … then we need to make sure it is immediately made so.”
She said that P&O workers “deserve more” than what happened to them.
“This is a disgraceful way for a Dubai-based conglomerate to treat British workers in this country,” she added.

. Protesters leave the P&O site at the Port of Hull, East Yorkshire
Protesters leave the P&O site at the Port of Hull, East Yorkshire, after P&O Ferries suspended sailings and handed 800 seafarers immediate severance notices. Picture date: Friday March 18, 2022. Photo: Danny Lawson

. Protesters gather outside the Port of Hull to demonstrate against P&O Ferries
Protesters gather outside the Port of Hull to demonstrate against P&O Ferries on March 18, 2022 in Hull, England. P&O yesterday suspended all ferry crossings from the UK to France and the Netherlands and made all 800 crew members redundant without Union consultation (Photo by Ian Forsyth/Getty Images) Photo: Ian Forsyth

. Labour MP for Kingston upon Hull East, Karl Turner (centre) speaks to protesters outside the Port of Hull
Labour MP for Kingston upon Hull East, Karl Turner (centre) speaks to protesters outside the Port of Hull,. Downing Street has said ministers have asked the Insolvency Service to investigate whether P&O complied with the notification requirements before making staff redundant. Photo: Danny Lawson

. Ed Miliband MP for Doncaster North, addresses protesters
Ed Miliband, Shadow Secretary of State for Climate Change and Net Zero and MP for Doncaster North, addresses protesters as they gather outside the Port of Hull to demonstrate against P&O Ferries. (Photo by Ian Forsyth/Getty Images) Photo: Ian Forsyth

9. Protesters outside the Port of Hull
Protesters outside the Port of Hull, East Yorkshire, after P&O Ferries suspended sailings and handed 800 seafarers immediate severance notices. Photo: Danny Lawson

10. Protesters stand outside the P&O building at the Port of Hull
Protesters stand outside the P&O building at the Port of Hull, Photo: Danny Lawson