As P&O parent company DP World reported first-half profit of $721 million (£598 million) this week, up 52% on the same period last year, TUC general secretary Frances O’Grady said: "No company should be allowed to profiteer from mistreating or underpaying their staff.
Refresh - the P&O Ferries scandal:
In March P&O sacked more than 700 members of staff and planned to replace them with agency workers.
Company CEO Peter Hebblethwaite later admitted to MPs that his firm had broken UK law as it failed to consult with unions before making mass redundancies.
Since then, in response to widespread rail strikes, the UK government overturned its ban on employers using agency workers to replace striking staff.
By overturning the ban, O’Grady said: “Now they [ministers] too are using the P&O playbook.
"But rather than bringing forward an employment bill to crackdown on rogue employers, the Conservative government is picking a fight with unions to reduce workers' bargaining power."
Luxury London department store Harrods made headlines this week for reportedly becoming the first company to use the new law to replace its striking workers with agency staff.
Trade unions have been campaigning against the lift of the ban on using agency workers for this purpose since the change was first proposed, warning it would be unsafe and undermines British workers’ rights to strike.
Amidst rising inflation and a cost-of-living crisis in the UK, many sectors have witnessed strikes over the summer, with workers calling for higher pay.
A July report from the CIPD found that around half (53%) of UK employers believe the country is on the way to entering a new, more unstable period of employee relations.