Speaking at the STUC, the Scottish Labour leader said his party would change regulations if they were in power.
The company prompted outrage last month by sacking 800 船員, before replacing them with cheaper agency staff.
Speaking to the STUC Congress in アバディーン, Anas Sarwar said his party would immediately change regulations to ensure such a sacking could not happen again.
A general election is expected by the end of January 2025 遅くとも.
“Those workers kept their company going, kept our country going and demonstrated loyalty to that company and got no hint of that loyalty in return,” Mr Sarwar told delegates.
“For them to be callously sacked over ズーム, for many of them to be ambushed on ships, faced with individuals in balaclavas and handcuffs is disgusting, it is shameful, it is criminal and it cannot be allowed to happen again.”
彼が追加した: “It’s also a powerful reminder about why trade unions matter, but also a powerful reminder about why political change matters in this country too.
“The next Labour Government – on day one – has to make sure that the law is robust enough and on the side of the workers, not the employers, to make sure that never, ever happens again.”
Mr Sarwar also called for P&O bosses to be “prosecuted”, pushing for them to “face the most severe of consequences for their actions”.
The Scottish Labour leader was speaking while a P&O-run ferry was adrift in the アイリッシュ海 due to a “mechanical issue”.
His comments come the day after STUC president, Pat Rafferty, used his speech to call for P&O Ferries chief executive, Peter Hebblethwaite, to be jailed.
“There is something seriously wrong with our society when a company CEO like P&O can swan into a Westminster parliamentary committee and openly state that he broke the law – and worse still, he’d do it again,” Mr Rafferty said on Monday.
“What that clearly demonstrates is how useless the law is. There is no deterrent to companies like P&O who are getting away with destroying people’s lives.
“The law needs to change. Peter Hebblethwaite should be struck off the directors’ register and put behind bars.
“That would send a clear message to employers, act irresponsibly towards workers and face the possibility that you will be jailed.”